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After the success of The 2^nd International Conference of Water Resources Development and Environmental Protection 2017 (ICWRDEP 2017) two years ago, we came with the next conference which held every two years. The 3^rd International Conference of Water Resources Development and Environmental Protection 2019 (The 3^rd ICWRDEP) Water Resources Engineering Department, Faculty of Engineering, Universitas Brawijaya was conducted on October 12-13, 2019. The Conference was organized by Water Resources Engineering Department - Faculty of Engineering - Universitas Brawijaya collaborated with Ministry of Public Works and Housings Indonesia, Disaster Prevention Research Center Kyoto University Japan, National Central University Taiwan, Universiti Malaysia Pahang, Rajamangala University of Technology Thailand.

The main topic of conference is Multi-Perspective on Water-Related Challenges. And the subtopics are River Engineering and Management, Coastal Engineering and Management, Environmental Engineering & Sanitation, Water-Related Disaster Risk Reduction, and Water Resources Engineering and Management. The conference provide platform for researchers, engineers and academician to meet and share ideas, achievement as well as experiences through the presentation of papers and discussion. These events are important to promote and encourage the application of new concept of water resources development and techniques to practitioners as well as enhancing the knowledge of environmental protection with the current requirements of analysis, design and construction of any engineering concept.

List of committees, Photos are available in the pdf.

All papers published in this volume of IOP Conference Series: Earth and Environmental Science have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

The behaviour of flow due to nonlinear bends in piping networks involves the occurrence of contractions and turbulence that begin when approaching the upstream part down to the downstream part; these conditions are caused by collisions between fluid particles flowing with pipe walls in sudden direction changes. Though contractions and turbulence occur in all directions along the bends, the normal flow downstream of the bends occurs quite far after the bends. The elements that influence contraction and turbulence are velocities (U), number of slices (n), length of nonlinear walls (Li), sudden angle changes (α), coefficient of friction (f), acceleration of gravity (g), and the slope of the pipe base (I). A higher flow velocity in a pipe leads to farther laminar flow returns downstream of the bends, and a smaller flow velocity leads to the flow returning to normal downstream shortly after the bends. The simulations of this research involved a 10 m/s initial velocity with a 25.4 mm pipe diameter and the number of slices (n) = 2; normal flow was achieved at 22D after the nonlinear bend. With similar velocity and different diameters of pipes, the length of contraction, turbulence, and laminar flow were equal. This analysis is expected to provide optimal benefits for performance in the usage of nonlinear bends in activities related to piping networks, especially the primary network, which uses large-diameter pipes.

PDAM of the City of Buntok is the supplier of clean water needs for the areas of Buntok Kota, Hilirsper, and Jelapat Hamlets and Pamait Village. Population growth, water loss and utilization of discharge that has not been optimal have become obstacles in service. The aim of the research is to evaluate the existing distribution network and development plan until 2038 as viewed from the aspect of hydraulics and water quality using WaterCAD v8i software, as well as economic analysis to determine water prices. The available discharge is 10, 000 l/s. Simulation of the existing condition produces pressure and headloss gradient that meet technical requirements, while velocity did not meet technical criteria. Water requirements for 2038 need an additional Water Treatment Plant with capacities of 30 l/s and 20 l/s. The simulation of development results met the technical requirements, being 0.3-4.5 m/s, a headloss gradient 0-15 m/km, and pressure of 0.5-8 atm. Further, the hydraulic model was used to analyse the concentration of residual chlorine. Injection at the tank inlet amounted to a constant 0.4 mg/l. Simulation of produced residual chlorine met the requirements from 0.383-0.395 mg/l. Economic analysis resulted in a water price of Rp. 6, 100.00/m3, BCR 1.23, IRR 12.14 %, and BEP of 11 years. Based on the willingness to pay being Rp. 4, 200.00/m3, the value of required government subsidies is Rp. 13, 905, 747, 800.

Decreasing river water quality due to the environmental conditions around the river can cause changes in the value of river benefits and endanger the environment. Thus, it becomes necessary to improve river water quality management by monitoring water quality. The purpose of this study is to model predictions of water quality conditions. The method is by analysing the parameters of water quality (BOD, COD, DO, pH, temperature) influenced by rainfall, catchment area, and land use. Data analysis was performed by the artificial neural network (ANN) method, using the Matlab R2014b software. In the process of network development, the most effective model was obtained with a variation of 75% training data with 5 hidden layers and a maximum epoch of 2000. From the results of the model, the relative errors (RE) for BOD, COD, DO, pH, and temperature were found to be 7.80%, 6.33%, 6.83%, 1.92% and 1.05% respectively, with an overall average of 4.79%. Because this RE value is quite small and less than 5%, it can be concluded that the artificial neural network method is quite effective for monitoring water quality conditions in the study area.

Groundwater is one kind of clean water resource. The increased development of human activities, such as agriculture, industry, and settlements, has a cumulative impact on groundwater conditions. The main purpose of this research is to assess the intrinsic vulnerability of shallow groundwater to pollution in the City of Pasuruan. The utilized method in the intrinsic vulnerability assessment of shallow groundwater is the GOD method, by utilizing geoelectric data. The parameters used in the calculation are aquifer layer type (G), soil layer type above the aquifer layer (O), and ground water depth (D). The City of Pasuruan has a moderate to high index of intrinsic vulnerability, and shallow water at the study site is categorized as vulnerable to pollutants.

Temef Watershed is located in the Benanain River Basin with a catchment area of 551.50 km². River characteristics in the Temef Watershed are influenced by three main river streams from upstream to downstream. Conventional collection of data on watershed characteristics requires a relatively long process and time. However, when based on Geographic Information Systems (GIS), the cost and time will be more efficient. The floodwater level is affected by the amount of rainwater runoff that occurs in the Temef Watershed. The amount of runoff depends on the level of soil permeability and land cover. To determine the level of soil permeability, hydrogeological maps are used. Based on this, a study of the characteristics of flood waters from GIS-based hydrogeology is needed. The analysis method used ArcGIS overlay on hydrogeological maps, while data on watershed characteristics used the Archydro and HEC-GeoHMS features. The results of the analysis showed a level 3 permeability type with limestone lithology, solid volcanic breccia, sandy marlene, conglomerate, and alluvium consisting of sand and gravel having moderate to high permeability. The metamorphic and basalt rocks have low to moderate permeability and the scaly clay has low to very low permeability. This condition causes runoff that turn into flood streams.

Grawan Dam was built in 2004 to supply irrigation water and raw water. Lately, the dam has experienced various symptoms of damage to the overflow structure due to hydraulic behaviour and the possibility of overtopping of the dam, which endangers the stability of the dam. Therefore, it is necessary to evaluate the overflow structure system based on the current hydrological conditions and to review the slope stability. In this study an evaluation was carried out covering the safety of the slopes as well as the safety of the overflow building system. Dam slope safety was reviewed based on seepage and slope stability. The stability of the overflow structure security system was evaluated in normal and earthquake conditions. The results of the hydrological analysis on guard height, seepage that occurs safely to permit discharge, and slope stability showed 100% safety from permitted safety factors, and on hydraulic conditions resulted in proposed improvements for Vlugter ponds, transition channels, and energy dampers with planning for Q100, Q1000, and QPMF. Analysis for the stability of the overflow structure showed that it is safe against rolling and sliding, and meets the eccentricity and carrying capacity of the soil, being 100% safe.

A spillway is one of the most important features of a dam. It should be able to allow flood discharge to flow and keep its structure stable. The force impacting a spillway is great; hence, it needs a proper design. The design philosophy of a spillway is to maximize its discharge while keeping the water level in the dam low. The discharge capacity of a spillway is mostly predicted based on empirical data derived from idealized conditions with laboratory experiment. To determine actual capacity, a physical test model is usually utilized. However, a physical model needs large amounts of space and time to prepare. Computational Fluid Dynamics (CFD) offers an interesting method to predict spillway capacity with less time and resources. In this paper, a simulation of flow over an Ogee spillway was performed using the open-source CFD platform called OpenFOAM. The flow is simulated based on the Volume of Fluid (VoF) method to resolve the dynamics of free surface. The simulation results show a good agreement with experimental measurements and the USBR method of calculation.

The supply of water for human consumption starts with the abstraction of 'raw' water from various sources. Most of these facilities convey raw water by pumping it directly from rivers via lateral channels to nearby water treatment plants, but this is badly affected by debris and sediment clogging at the intake structures. Lateral intakes are actually special cases of river bifurcations, where the channel naturally divides into two different branches, each carrying part of the flow and sediment. Many researchers have completed studies on bifurcations/diversions to understand the behaviour of water flow and sediment transport. However, a complete understanding of the phenomenon, especially in relation to secondary flows and vortices, is lacking up to this day. In fact, if this can be overcome, it will greatly contribute to the fundamental study of hydrodynamics at asymmetric fluvial bifurcations as well as in optimal design of diversions. Thus, the distribution of water flow in both main and lateral channels requires further detailed investigation. A review of the current state of research is discussed in this paper, with the objective of identifying the grey areas and gaps specifically in the investigation of complex turbulent behaviour of flow structures in open channels with lateral diversions.

Riverbeds in the Mt. Merapi area are dominated by gravel originating from Mt. Merapi. The 2010 Mt. Merapi eruption has formed a riverbed consisting of sediments of various size. Since then, the morphology of the rivers has changed dynamically, depending upon the natural and the anthropogenic factors. Most of the rivers drain into the Progo River, whereas the main river system of Progo River drains into the Indian Ocean. The dynamics of the tributaries of volcanic rivers along the Progo River are the major concern to identify the capacity of the tributaries against potential lahar flow disasters that may occur. This paper presents the results of a series of observations of several tributaries of the volcanic rivers, taking into account the natural flow phenomena as well as the sediment mining activity along the river under investigation. The investigation included the hydraulic simulation, which employed a numerical model. The results of the simulation showed that the downstream part of the Progo River is influenced by sediment from Mt. Merapi through its tributaries. These also suggest cost-effective river tributary maintenance to mitigate the risks of lahar flow disasters.

The issue of the sedimentation problem of reservoirs has been growing significantly during the last two decades, particularly in areas where human activity increases pressure on the land. However, some researchers believe that such situation is also (partly) affected by the significant shift in hydro-meteorological conditions, accompanied with higher rainfall erosivity and hence an increase in land erosion. Various efforts have been suggested to control the erosion process, whether by sediment control at the catchment area or placing a ground sill and/or check dam in the stream. However, additional activities to remove sediment from reservoirs through sluicing, flushing, and dredging are often still necessary. This paper deals with the evaluation of the effectiveness of flushing at different timings. The results showed that the uncertainty of the sedimentation process and the hydrograph inflow characteristics are dominant factors affecting the problems. A further recommendation is to determine the procedure for establishing reliable advance timing that is considered most efficient for carrying out the flushing activities.

This paper presents the hydraulic flow system in a fishway to simulate the flow of a pool-type fishway. A fishway is a waterway to allow some fish species to pass by a human-made obstruction in a river or stream. The construction on the river, which has no fishway, will impact the river ecosystem balance. The purpose of this research is to give an alternative to reduce negative effect on the river ecosystem because of the obstruction. The velocimeter and the flow type in fishway must be able to be passed by the fish. In a kind of the pool-type fishway, there is an orifice in the bottom that has a potential supercritical flow before it becomes subcritical flow. The purpose of this experiment is to identify the surge in the pools of the fishway. The physical model of the pool-type fishway in Sembayat Barrage, Gresik was created to analyse the hydraulic condition of the flow in the fishway structure. The velocity has a greater value than the permissible velocity of the fish, and thus several fishways are not able to function optimally because the fish refuse to swim through the fishway. From the results of the study, it can be concluded that the velocity can be reduced by adding baffles at the downstream part of the orifice.

The weir design process not only considers the location, dimensions, strength, and durability of the weir structure, but must also be consider the effect on the flow characteristics in the river after the weir, especially related to the flow velocity characteristic around the weir. The water level will rise and affect the flow velocity downstream of the weir. Because of the fall of water, the velocity will greatly increase and the river can erode. The weir construction on the Batang Asai River, specifically located in Sarolangun, Province of Jambi, has unique conditions that cause the velocity of water after the weir to increase. Several alternatives will be analysed as solutions to deal with changes in flow velocity. The alternatives are groundsill, riverbed normalization, and river crossing widening. It was found that the alternative of river widening showed a significant reduction in flow velocity.

In the Brantas River System, Sengguruh is the first reservoir in the direction of the river flow. This reservoir functions to protect Sutami Reservoir from severe sedimentation. The effective storage capacity was about 24% of its initial storage. In order to restore the storage, dredging work at Sengguruh Reservoir must be carried out over the course of the year. To support the dredging, it is necessary to carry out technical work so that sediments in the temporary spoilbanks can be immediately hauled to another place and then are ready to be refilled. Hauling can be done optimally if the sediment condition in the spoilbanks is quite dry. Therefore, it is necessary to know how horizontal drainage can affect the sediment water content in the spoilbanks.

This paper presents a study carried out to assess the accuracy of several sediment transport functions commonly applied in HEC-RAS 4.0 against data from the sediment flushing of Wlingi reservoir in 2016. Another aim of this assessment is to evaluate the viability of selected transport equations to simulate riverbed changes during the sediment-flushing event. Thus, the best scenario of sediment flushing could be determined according to their efficiencies. The overall accuracy of the transport function indicated by RMSE values in descending order were those of Laursen-Copeland, Ackers and White, Meyer-Peter and Müller, and Wilcock formulas, when applied to the observed data. The study also indicated that Laursen-Copeland formula had parameters that were commonly well-characterized by the riverbed of Wlingi reservoir. Further, it was suitable to be utilised to assess the achievement of sediment flushing in Wlingi reservoir, while others seem less satisfactory.

Among natural hazards, droughts are known to cause extensive damage and affect a significant number of people. Droughts also have wide impacts across the economy, society, health, and education. This research is expected to be a reference to estimate the existence of droughts. After performing the calculation of drought indices, a drought distribution map was made using a Geographic Information System (GIS). The results showed that the worst drought occurred in 2013 to 2014. The average comparison between the discharge data and the level of decile data of both rain stations is 50%. It is evident that the discharge and decile-level data have good conformity. The result of the analysis, when associated with the incidence of El Nino, has a suitability of 32%, which could be due to other factors that affect rain conditions in the study location. Based on the results of the analysis of the annual trend of rainfall accumulation, the year when climate change initially occurred was in 2003. From 1990 to 2003 the drought distribution conditions tended to be "Dry" to "Very Dry", whereas from 2003 to 2014 the drought-level distribution conditions were likely to be "Dry" to "Very Dry".

Pervious concrete is an alternative to reduce surface runoff in urban areas. To examine effect of different materials on the void ratio of pervious concrete is studied in order to evaluate the efficiency of pervious concrete solving surface runoff problems. Various materials have been used in mix proportion of pervious concrete. Different size of aggregate, the use of supplementary material for cement, recycled aggregate as an alternative to replacing natural coarse aggregate, and fiber usage were utilized in a series of experiment to evaluate the value of void ratio that greatly affects the effectiveness of pervious concrete to cope surface runoff in urban areas. The result shows that the size of aggregate strongly affected the void ratio of pervious concrete, while the effect of the use of supplementary material for cement in pervious concrete to its void ratio was not significant. However, pervious concrete made of recycled aggregate proved to have a higher void ratio compared to pervious concrete using natural coarse aggregate. When utilizing fiber in mix proportion of pervious concrete, the higher rate of fiber reduced its void ratio.

Global Warming has had an impact on climate change, which has caused disturbance to the availability of surface water and the change in the allocation of irrigation water for agriculture. The agricultural sector is a sector that is vulnerable to climate change. Therefore, the provision of irrigation water must be adapted to climate change so that the supply of irrigation water for agricultural land is well maintained to increase food production. The method used in completing this research is the descriptive method, involving observations during the rainy season, first dry season, and second dry season, soil tests at the research site, and disseminating improvements to the provision of irrigation water, so that irrigation water is more efficient in usage and distributed at the right time at the start of the rainy season, first dry season, and second dry season. In distributing questionnaires and providing understanding of the occurrences of climate change, almost all stakeholders have understood that the provision of irrigation water must be refined and adapted to climate change. Dissemination has been carried out to all stakeholders including the government and relevant agencies. The government promises to change the irrigation water regulation policy in order to maintain food productivity.

High population growth in the area of East Jakarta has led to more construction of settlements, including in several areas of East Jakarta, which includes Jalan Pengantin Ali in Ciracas Sub-District. When very heavy rains fall in the rainy season, this place is often flooded, while in the dry season there is a scarcity of raw water or clean water. This study examines the application of sustainable drainage systems with the technique of making a retention pond as a flood control alternative. The purpose is to hold water runoff during the rainy season so that it does not enter the river directly, and so that some of the collected water could be used to meet the clean water supply needs of the people. The calculation of rainwater potential used the height of the monthly average rainfall. The retention pond capacity was determined by the pool simulation method during the rainy season. The planned flood discharge was calculated using the Nakayasu HSS method. The obtained results indicated a peak discharge value with a return period of 2 years that amounted to 8.84 m³/sec. The planned retention pond area is 6380.94 m², with a retention pond height of 4 m, a dike slope of 1:1, and the elevation of the overflow base being at an altitude of 38.5 meters above sea level (masl). From the results of the HEC-RAS 5.0.6 software, an optimal overflow width of 2 m was obtained, with an outflow discharge of 4.55 m³/sec and a pond volume of 19530 m³. With the retention pond, flood peak discharge could be reduced by 4.29 m³/sec. This will allow the flood discharge in the rainy season to be reduced and increased clean water needs in the dry season to be met.

A study of water balance in the Upper Konto sub-watershed was carried out to determine the potential for water availability and its use in the multisector water needs. Rainfall was converted into discharge using the F. J. Mock method, compared with the observed discharge, and calibrated with the Relative Error, Root-Mean-Square Error (RMSE), Nash-Sutcliffe Efficiency (NSE), and Correlation Coefficient (R). The potential for water availability was calculated based on an 80% dependable flow using the Weibull probability method with an amount of 22.41 m³/sec, equivalent to 706.622 million m³/year. The amount of water demand within a period of 25 years in scenario 1 (calculated based on data and increasing according to the growth rate) is 95.090 million m3/year, while in scenario 2 (based on the assumption that domestic, non-domestic, and industry demand increased while fishery, agriculture, and livestock demand remained constant) is 93.419 million m³/year. The results of the water balance analysis showed that the potential for water availability is sufficient for all multisector water needs, or indicates a surplus condition for 25 years (2017-2042).

The quantity of rain that falls on the earth cannot be known with certainty. Floods and droughts due to a small quantity of rainfall are frequent events in some areas of Indonesia. The depth of rainfall at a certain time can be anticipated with accurate information. Along with rapid advances in technology, the forecasting of patterns of rainfall can be performed by artificial intelligence models, using historical data for the climatological parameters. The aim of this study is to predict rainfall depth based on climatology data. There are three categories of data that were obtained using NeuroSolutions for Excel: monthly, daily and hourly data. The input data are temperature, pressure, duration of sunshine, and humidity. The output data is rainfall depth. Based on the results of running calculations on monthly, daily, and hourly data, it was indicated that monthly, daily, and hourly data have relative errors of 11.49%, 8.49%, and 19.32% respectively.

Reservoir operation is strongly influenced by water balance conditions in the catchment area. The amount of inflow, reservoir capacity, and water requirements are major factors in creating reservoir operation rules. The purpose of this research is to obtain the extent of the reliability of parallel reservoir operation with simultaneous execution by utilizing water transfer from wet to dry watersheds. Reservoir operation rules were derived by utilizing the storage capacity of the two reservoirs with two spillways and two separate water demands in the downstream parts. The various parameters applied for the operation rules are expected to optimize the operation of the reservoirs.

On June 3, 1994, an earthquake located 200 km south of the island of Java triggered a devastating tsunami and caused losses of life and materials around beaches in the Jember, Lumajang, and Banyuwangi Regencies. It is highly important to study the process of tsunami occurrences, especially at Puger Beach, Jember. Thus, the main purpose of this study is to understand the mechanism of tsunamis in Puger Beach. Tsunami numerical simulation was performed using the Delft3D model to calculate the propagation of possible future tsunamis. Bathymetric data obtained from GEBCO_08 were utilized in this study. The tsunami model was validated using the survey data of the tsunami on June 3, 1994. Tsunami simulations were successfully performed in this study. From numerical simulations, it was shown that the fault model characteristics utilized in the model directly affected the tsunami height. Just after the initial surface elevation, the wave height decreased and the tsunami propagated at sea. As the wave propagated from offshore to shallower area, the tsunami height increased until reaching the maximum tsunami height in coastal areas such as Puger Beach. Tsunami mechanisms are clarified from both numerical simulations.

Canopy characteristics have a significant influence on the process of canopy surface wetting and water canalization into the canopy reservoir. Canopy surfaces that have increased wetting until the canopy is saturated will describe the process of rainfall redistribution that occurs throughout the canopy. Canopy wetting until saturated or the canopy wetting index (β) is an indicator of rainfall redistribution by a canopy. Canopy reservoir filling can occur after the canopy surface per unit area has been completely saturated. This research was conducted with changes in rainfall intensity (R), leaf slope (α), canopy porosity, and canopy flow distribution (Tf) on Artocarpus heterophyllus. This study found that the rainfall redistribution process was strongly influenced by leaf characteristics, depth, and rainfall duration. Leaf characteristics, especially leaf inclination, will create a pattern of water canal from the canopy surface to the canopy reservoir. The leaf inclination characteristic will increase canopy wetting across the canopy surface simultaneously, but will not make water flow uniformly to the canopy reservoir.

Reduced water availability toward water needs is an indicator of the occurrence of a drought. Droughts have received greater attention from the Government of Jember Regency in the form of management directions for drought disaster areas. The location of this research is the Bedadung River Watershed, with 13 rain posts located upstream of the Rowotamtu AWLR Station. Drought analysis used the Palmer Drought Severity Index method in the form of an index that informs the level of drought in an area. The results of the study showed that drought with extreme dry classification occurred from June to October with drought index values ranging from -1.820 (June average) to -14.140 (October average). Patrang, Jelbuk, Arjasa and Panti Sub-Districts are areas that have experienced droughts with a duration of 5 months. The Palmer method meteorological drought index and hydrological drought index (value of AWLR Discharge Standardized Box Cox Transformation (Z)) have a unidirectional relationship and a very significant relationship, with the Pearson correlation coefficient being r = 0.905.

Declining potential of water resources and the highly increased exploration of water resources along with highly increased needs in society demand the analysis of water balance of the Gandong Watershed in Magetan Regency. Analysis results showed that surface water availability that comes from discharges, springs, and drilled wells is 35.144 m³/s in the dry season, 48.050 m³/s in the low season, 59.833 m³/s in the normal season, and 78.163 m³/s in the peak season. The availability of subsurface water is 163.650 m³/s. The surface water requirement of Gandong Watershed is 183.580 m³/s with 55 irrigation areas, and the subsurface water requirement is 118.990 m³/s. The highest surface water deficit is in the Jejeruk Irrigation Area, with 13.680 m³/s or only 1.23% of the needs met in December (dry season), and the highest surplus is in the Gemblung Irrigation Area, with 10.430 m³/s or 100% of the needs fulfilled in February (peak season). Water balance evaluated by the Water Evaluation and Planning (WEAP) Software showed only 10 irrigation areas met 100% of the demand. Subsurface water balance is at a surplus condition from January to December. Land water balance is at a deficit condition from May to December.

Puger Beach is located in the south Coast of Java Island which is directly facing the Indian Ocean. The ease of the ship to sail is influenced by the conditions of water in the port which caused by tides. The elevation of the crest of a breakwater is determined by the maximum high water level, while the depth of the shipping lane / port is determined by the minimum low water level. The purpose of this research is to evaluate the breakwater performance by analyzing the surface water level and flow velocity caused by tidal wave in Puger Beach using Delft3D-Flow. The bathymetry data obtained from BIG (Geospatial Information Agency of Indonesia) were utilized for the simulations. Tidal observation results from the previous study were used to validate the model. Two scenarios of breakwater layout were simulated. Spatial variation of flow velocities in the highest tide, the minimum ebb, and representative time steps for both cases are presented. It is shown that using the modified layout of breakwater, the flow velocities become smaller and more stable than that of the existing layout. Using breakwater in the right and left hand side of estuary, high velocities are able to be reduced. Based on the flow velocity pattern in five observation points and the water level, it is confirmed the modified breakwater layout of is more effective than that of the existing one.

The "user pays" principle is one of the principles of Integrated Water Resource Management. Water price should be set optimally, high enough to complement subsidies, but within the ability of users to pay for the water. This paper discusses the optimization of the water price for public water supply by considering the dominant parameters related to operational costs, government subsidies, and the ability to pay. The study location is the Jatigede reservoir, located in the Province of West Java with an effective reservoir volume of 877 million m³, and supplying public water supply at a rate of 3.5 m³/s. To investigate the feedback loop of the complex system of water price optimization, the system dynamics approach was applied. The study results showed that the water tariff for raw water reaches a numerical balance and can meet the annual operation and maintenance costs by up to 100%. The results of the analysis of the system dynamics model showed that the optimal price for raw water supply is lower than the price of raw water in other river basins.

Every year downstream area such DKI Jakarta city suffers from flood and it could disturb the economic life. High sea level, increasing number of rains, land subsidence, and conversion land use into built up area around upstream caused some damage flood in downstream area. To minimize the impact, the government of DKI Jakarta Province already constructed 36 polders system since 1973 and 11 polders planned to construct. Some of those polders have retention pond and other components to support the system. Those built up polders needs routine maintenance according to its budget in order to keep its function. Guideline to allocate budget for each polder's yearly maintenance not yet available. This research analyses indicators that give impacts to polder's services by using PLS and PCA Method, which based on 160 samples of questionnaire and result of site survey. As an object of this research, 8 polders in DKI Jakarta which have retention pond, pumps, water gate and trash rack are chosen. They are Polder Grogol, Polder Teluk Gong, Polder Melati, Polder West Setiabudi, Polder Pulomas, Polder Tomang, Polder North Sunter and Polder South Sunter. As a result, there are 23 indicators that affected in service index of polder system.

Irrigation plays an important role for increasing agricultural production in order to achieve national food sovereignty. However, in reality, requests of funding for the purpose of irrigation network management from year to year are not always fulfilled according to needs. As such, to resolve this issue, it is necessary to determine improvement priorities for repairs of irrigation assets so that management may be optimally carried out. The aim of this research is to determine and analyse the improvement priorities of irrigation assets in one of the irrigation areas of Madiun Regency. This study utilized the modified Irrigation Network Performance Evaluation Criteria and Weightings for the year 2018. In addition, statistical tests as the Kruskal-Wallis and Mann-Whitney tests were utilized, as the obtained data were in the form of rankings. Google Earth and ArcGIS software were utilized to facilitate the understanding of the conditions and management of all the assets. The required data was the inventory of the irrigation network. The results of the study showed that the Kedungrejo Irrigation Network has 10% of irrigation assets in very good condition, 37% in good condition, 49%, in fair condition, and 4% in poor condition. The highest ranking (ranking 1) was for the spillway, while the lowest ranking (ranking 82) was for a bridge.

The existence of irrigation in Indonesia is commonly quite influenced by environmental and social cultural characteristics, which the people have lived by and developed for a long time. Many factors cause changes in the pattern of water availability, which increases competition among stakeholders, as in the Sempor irrigation system area. It has four main dams, which are the Bojong Dam, Watubarut Dam, Rowokawuk Dam, and Sindut Dam; it provides approximately 5900 ha of services and receives supplies from the Great Sempor Dam (38 million m3). Currently there is a decline in the function of this dam due to sedimentation, making operational services less optimal, especially during the dry season. The methodology of this study is to perform water optimization for the balancing of water in the irrigation area. Meanwhile, the implementation of the water supply on the field considers the calculation of water availability, space, and time. In practice, the operation of water supply is held by a group system in the secondary blocks. In certain conditions, the water rotation in tertiary channels was performed by local cultural wisdom.

Shape factors of recharge wells that have existed in various forms can be seen in terms of the absorption and the value. The development of existing recharge wells considers their various shapes and values. The condition factor 5b, according to Dachler (1936) and Sunjoto (2002), needs to be examined. The shape factor is the coefficient of dimension planning, which takes into account the perimeter, area, volume, and water level of the recharge well. The permeability coefficient is very important. An experiment on the field involved three recharge well models in a flat base impregnation, testing the porous wall (L) and well radius (R). The aim of this research is to investigate the shape factor values of the three recharge well models whose upper walls are made of concrete pipes with diameters of 0.6 m, 0.8 m, and 1.0 m. The height of the porous wall varies from 0.3 m, 0.7 m, to 1.0 m. In this study, the results showed that the shape factor simultaneously influenced the height of the porous wall (F = 22.49 > F table = 5.59; P < 0.05). However, there is a positive correlation between the change in the shape factor and the height of the porous wall on a flat base for the recharge wells (R² = 0.79).

An accurate determination of water availability of Amprong River has an important role in the planting system to support the agricultural production process in the Kedungkandang Irrigation Area, because if the availability of water is not precisely determined, there will be an error in regulating irrigation water. To overcome these problems, a good analysis system is needed. One of the time-series models is the ARIMA (Autoregressive Integrated Moving Average) model. The model was built by discharge data from 9 periods from 2008/2009 to 2016/2017, and its purpose was to predict the discharge of the 2017/2018 period. There were only five models feasible for use. The best model is the ARIMA model (2, 0, 1) (1, 2, 1)³⁶ with values of MSE = 22.90; KR = 6.00; MSD = 8.05; MAD = 2.04; MAPE = 18.53; and MPE = -8.98.

Sugarcane farmers in Lumajang in East Java Province have a strong preference of using furrow irrigation instead of sprinkler irrigation. To evaluate the possibility of smallholder sprinkler irrigation as an alternative water-saving irrigation method, the aim of this research is to examine the socio-technical dimension of current irrigation practices of smallholder sugarcane farmers, emphasizing the extent of farmer perspectives and knowledge. As comparison to furrows, a smallholder sprinkler system was designed and evaluated. The sprinkler was expected to fit smallholders' acreage, has low investment costs, is easy to build by locals, and is easy in its operation. The responses, perspectives and expectations of farmers to this smallholder sprinkler system are also discussed. The results indicated that smallholder sugarcane farmers perceive furrow irrigation as the best and low-cost irrigation method. They have already spent money on furrow irrigation investment; however, that investment was seen as a burden for their budgets because smallholders perceived sprinkler irrigation as an expensive irrigation method. In addition, the sprinkler could not satisfy their main expectation because it delivered less water than furrows, meaning the soil was not saturated. This mind-set underlines the slow acceptance process of a relatively new irrigation technology implementation for smallholders in Indonesia.

Inundations occur and become problems in the City of Palu. Inundations occur due to outdated drainage systems, high levels of sedimentation, rapid urban development and topography that tends to be flat. The offered alternatives are rehabilitation of existing drainage channels, storage pond equipped with an automatic valve door, rainwater harvesting and gully plugs. Rehabilitation is performed by adjusting drainage depth, with consideration of the shallow groundwater in the area. For rainwater harvesting, the capacity of rain barrels varies from 350-1050 litres, and they are equipped with reservoir wells. With combinations of these alternatives, the inundation reduction effectiveness of catchment area (DTA) 1 is 93.5% and 99.6% for DTA2. Comparing the results to gully plugs, the effectiveness of inundation reduction in DTA1 is 81% and in DTA2 is 98.9%. The Budget Plan for rainwater harvesting varies depending on the capacity of rain barrels, ranging from Rp. 1, 492, 505.00 to Rp. 2, 692, 505.00. Gully plugs also vary in costs from Rp. 556, 000.00 to Rp. 808, 000.00, depending on the size of the gully plug. The first alternative is chosen by the combination of drainage rehabilitation, construction of a storage pond equipped with an automatic valve door, and rainwater harvesting. This is because the reduction effectiveness is greater and the rainwater harvesting maintenance is easier.

Rainfall data is the main input data for use in hydrological analysis, especially for planning purposes. Rainfall data is usually obtained from observations through rain stations. However, the availability of rainfall recording stations is sometimes very limited and located far from the project location. Water resource projects often face this obstacle. A technique is needed for estimating rainfall data using rain data from remote sensing through weather satellite data information providers. Since rainfall data from satellites is not the real amount of measured rainfall on the land, the rainfall data from the satellite must still be evaluated as to whether it can be directly used to represent the rainfall data of a region. The aim of this study is to evaluate the validity of NOAA CPC daily total precipitation data by comparing it to measured rainfall data and to analyse the lag time using the cross-correlation method. The results showed that the NOAA data has a lag time of +1 day over Lombok Island. The rain estimated by NOAA positively correlated with gauged rainfall on the next day. However, the performance of the NOAA data was very poor and for prediction purposes, the data still need to be calibrated.

Sustainable management in water resources development strategies depends on the knowledge of phenomena of changes in land use in the river basin as a significant tool in understanding the interactions of environment and human activities. Changes that occur within a certain period on the land cover or land use impacts the basin characteristics, which will ultimately affect river basin management. This paper studies the change of land use in the Lombok river basin in Indonesia based on the Moderate Resolution Imaging Spectroradiometer (MODIS) land use/land cover data version 6 from the years of 2001, 2010, and 2016 which were derived using MODIS Terra and Aqua reflectance supervised classification data. Land use data was then classified into fifteen land use categories according to SWAT classification. QGIS and MapWindow software were applied to analyse the features of land use in the study area, and the SWAT simulation model was applied to simulate the impacts of changing land use in the sub-basin. The study concludes that areas with occurrences of changes in land use impacted the river runoff in the sub-basin. Analysis of river basin land use, when combined with simulation in water resources management, will contribute to optimal and sustainable river basin planning.

The purpose of this study is to determine the condition of water quality, trophic status, abundance and type of phytoplankton, and pollution load, as well as to formulate a conservative effort for reservoir management based on Lahor Reservoir conditions in 2017. The data needed for water quality analysis are total P, NO3-N, NO2-N, NH3-N, BOD, DO, TSS, and pH; hydrological and reservoir data such as rainfall data, the volume of the reservoir, reservoir catchment area, and Lahor reservoir outflow; as well as data on abundance and types of phytoplankton. The results of the water quality analysis of the Lahor Reservoir showed that it did not meet Class II water quality standards and trophic status, being eutrophic to hypereutrophic, which means the Lahor Reservoir has become polluted. The abundance of phytoplankton that occurs in the Lahor Reservoir exceeds the limit of the phytoplankton abundance that has been determined and is dominated by Microcystis blue-green algae. Therefore, the recommended efforts are bioremediation techniques, regulation of reservoir operation patterns, application of the Trophic Level-Based Aquaculture (TLBA) system, and introduction of rotifer zooplankton.

The high rates of erosion and sedimentation as the impacts of changes in land use cause the problem of sedimentation. The aim of this research is to analyse erosion and sedimentation in the Upper Citarum sub-basin, which will impact the life time of the Cieunteung retention basin. The SWAT model was used to simulate the hydrological process and erosion mechanism by using the formula of MUSLE. Based on the results of simulation data, the highest average erosion equalled 1, 094 tons/ha/year in 2013 while the lowest average erosion equalled 71.16 tons/ha/year in 2009. The results of SWAT model calibration in 2008-2018 were R² = 0.89 and NS = 0.95, which means the model performance is categorized as very good. The simulation results showed the anticipative indicators of watershed disaster, as the erosion hazard index in terms of land cover and the coefficient of river regime in terms of water availability, have a very close relationship and positive correlation with the average of R² = 0.8. The incoming sediment to the Cieunteung retention basin is 105, 418 ton/year or 72, 551.961 m³/year. By using sediment trap efficiency with a value of 4.37%, this research estimated that the dead storage capacity of 113, 670.3 m³ will be filled with sediments in 35.87 years. Furthermore, the long-term retention basin conservation effort by land terracing can reduce total sediments by 22% to 81, 948 tons in 2018, and thus the life time of the Cieunteung retention basin becomes 46.15 years.

Global climate change occurs because of the addition of absorbing gases into the atmosphere, which can be interpreted as the greenhouse effect. Changes that occur in temperature will be followed by changes in other climatic elements, including rainfall, solar radiation, air humidity, and wind speed. The purpose of this study is to determine the sensitivity of potential evapotranspiration calculation methods to climate change and to determine the diversity of results based on differences in the calculation structure and the needed data. The utilized methods to estimate the sensitivity of potential evapotranspiration (ETp) to climate change were the Thornthwaite, Blaney-Criddle, FAO without correction, Makkink, Ivanov, Hargreaves-74, Modified Penman, and Penman-Monteith methods. The analysis was carried out using climate data from three climatological station locations in Central Sulawesi, which are the Singkoyo, Kulawi, and Bora Stations. The calculation results showed that the Thornthwaite and Blaney-Criddle methods were relatively the most sensitive to temperature changes, followed by the Penman-Monteith, Ivanov, Hargreaves 74, and Modified Penman methods. The FAO and Makkink methods showed relatively little sensitivity.

Since 2015, collaborative research conducted by Indonesian and Japan scientists has initiated the installation of small X-band Multi-Parameter (X-MP) radars to mitigate the occurrence of rainfall-induced lahar in three active volcanoes in Indonesia and Japan: Merapi, Sinabung, and Sakurajima. This paper discusses the technical aspects of data acquisition, processing, and performance of the X-MP radar at the Merapi and Sakurajima volcanoes by comparing the estimated rainfall intensity acquired by the radar to three empirical radar-rainfall algorithms. The algorithms are based on radar reflectivity factor (ZHH), specific differential phase shift (KDP), and differential reflectivity (ZDR). A new method of Constant Altitude Plan Position Indicator (CAPPI) interpolation by linear regression is also proposed for a more efficient computation. The first algorithm by Marshall-Palmer, which relies on ZHH, gave the lowest average and maximum rainfall values compared with the other algorithms for all rainfall event cases. On the other hand, the other two algorithms, which involve the MP of radar by Bringi and Chandrasekar and Park et al., gave closer rainfall intensity values with the estimated rainfall intensity acquired by the X-MP radar. These three rain rates give a closer temporal fluctuation when they are compared to the rain gauge-based rainfall intensity.

Peatlands are very vulnerable, and their existence must be maintained as stores of water and carbon stocks. Moreover, due to improper management, peatlands in Indonesia have degraded, resulting in various environmental problems such as fire, flooding, and subsidence. Drainage on peatlands that is not carried out properly causes the peat to dry out and even become vulnerable or flammable. The peat becoming dry on a large scale has the potential to increase subsidence and greenhouse gas emissions (such as CO2), which can contribute to local and global climate change. The management of peatlands in the cultivation area must pay attention to the unity of the peat area (landscape), including the existence of peat domes. The main parameters that need to be taken into account in land and water management in peat land are (1) Drainability Limits, (2) Subsidence, (3) Land Useful Life, (4) Adjacent Ecosystem Linkages, (5) Peatland Externalities, and (6) Priorities and Prevention of Massive and Disastrous Damage. Water management is one of the most important aspects in peatland management, which needs to be performed by water regulation so that the peat soil surface remains wet, preventing it from drought in the dry season and causing fires, and at the same time preventing flood disasters during the rainy season. Efforts to utilize excess water during the rainy season to cover the water deficit in the dry season need to be endeavoured to minimize wasted water.

Groundwater as a water resource has now become a complex national issue. Therefore, due to excessive groundwater abstraction, it is necessary to minimize the negative impact. This research aims to estimate groundwater level distribution and its possible use at the Faculty of Engineering of the University of Jember. A total path length of 392 meters was investigated. Field data was collected using a resistivity meter with the Wenner configuration method. In addition, the data obtained from the measurements were processed using RES2DINV software. The results showed that the distribution of groundwater lies at depths between 25.3-39.7 meters. Meanwhile, the potential use for aquifers is classified as moderate. This is based on the classification of groundwater potential, which indicated that the layers of soil at the site contain alluvium plains and coarse-grained to medium gravel and sand, with the addition of clay.

Fulfilment of drinking water needs is one of the government programs to support the achievement of the target of Sustainable Development Goals (SDGs). One of the important parameters in the fulfilment of drinking water needs is a good distribution system. The aims of this research are to create a design to analyse the hydraulic model of drinking water distribution. The utilized model involved the EPANET 2.0 software. The utilized data included land elevation, pipe distribution base map, population, and discharge. The results indicated that the existing design has not fulfilled the standards of availability, hydraulics analysis, and calibration. Therefore, there needs to be a redesign that fulfils all parameters. The results of the new design requires a two-stage development process for the new water distribution system, with the first stage to be executed in 2015-2020 and the second stage to be executed in 2020-2025. Hydraulic analysis shows that additional discharge is needed to increase pressure and velocity. Model calibration was performed by comparing simulated data with field data; the result of pressure calibration is 0.928 and the result of discharge calibration is 0.894. These two results indicated that the results of the simulation are highly correlated with the field conditions.

Pangandaran Regency is located in the Province of West Java and consists of the subdistricts of Parigi, Cijulang, Cimerak, Cigugur, Langkaplancar, Mangunjaya, Padaherang, Kalipucang, Pangandaran, and Sidamulih. The capital of Pangandaran Regency is located in Parigi Sub-District. The rapid growth in the area has resulted in increased water demands, which in turn has resulted in an imbalance between water availability and water needs. To restore the function of recharge areas, Pangandaran Reservoir was built in order to conserve water. In addition to its function to recharge, the reservoir can be used as a source of raw water supply for Pangandaran Regency. In its operation, the water collected in the reservoir must be used optimally to meet the needs of various sectors. To achieve this goal, a study of reservoir operations is needed. This study of reservoir operations includes analysis of rainfall, analysis of water availability using the F.J. Mock method and NRECA, analysis of reliable discharge, and analysis of needs for various needs such as irrigation and drinking water for the people. By using water equilibrium as well as minimum and maximum storage limits (effective storage), the fulfilment of water needs for domestic, municipal, and irrigation or industrial use can be known.

The intent of this research is to investigate the rainfall erosion index that has the highest correlation to the surface runoff volume and the amount of soil erosion. In addition, the aim of this research is to determine the effective rainfall erosion index to predict soil erosion based on observations. This research was conducted in a hydrology laboratory by using a rainfall simulator. The three methods that were used for analysing rainfall erosion were the formulas of EI30 by Bols, Utomo, and Lenvain. The result is expected to become a consideration in selecting the model of rainfall erosion index due to the rainfall factor as the input of soil erosion prediction. This research provides a temporary hypothesis for obtaining the value of the rain erosivity index with a different value from previous studies with EI30, which leads to the latest model for estimating and predicting from the Bols equation. Based on this research, the rain erosivity index was obtained with a predicting value and final equation of EI30 = 5.128 x (Rain)^1.26 x (Days)^0.47 x (Maxp)^0.53 x (High)^0.61 with the explained value from research analysis being EI30 = 5.128 x (50.002)^1.35 x (23)^0.47 x (622)^0.53 x (12)^0.61. Analysis was then performed with trial and error, and the conclusion of this research is a high rain erosivity index.

As a mass structure, the seismic performance of a specified dam is importantly necessary, especially in the area which earthquake likely occur. The purpose of this study was to determine the critical areas of specified dam under earthquake motion. The dam structure was analyses with shell meshed modelling in empty condition and normal condition (operation term), as well as the seismic analysis under earthquake motion. The dynamic response analysis was carried out using response spectral acceleration under Operating Basis Earthquake (OBE) and Maximum Design Earthquake (MDE) based on earthquake records. According to the analytical results from the dynamic analyses, it was found that the shell structure members of the dam heel in the upstream were having a very large bending moment. The analysis also showed that the shell structure members in the face of downstream slopes were significantly responded the seismic motion in some certain modes. These two areas of the dam have become the critical areas of the dam which needed to be addressed in strength design of the specified dam.

Rawabangun is one of the areas in the City of Toboali in South Bangka Regency that is often flooded. There is a main river that passes through the Rawabangun area, which is the Linei River. The aim of this study is to analyse alternatives that can be used in flood control in Rawabangun. The analysis was carried out with the 5.1 Storm Water Management Model (SWMM) and 5-year planned rainfall. There were 9 overflow points found on the channel, and the implementation of flood control is to be carried out with infiltration wells, retention ponds, and channel modification. The application of infiltration wells with a maximum of 1267 units can eliminate 8 overflow points. The application of 3 units of retention ponds with a maximum of 3 units can eliminate 5 overflow points. Changing the channel depth to 4 m can eliminate all overflow points but is not relevant to be applied.

Floods that occur in the Upper Citarum River Basin are generally caused by flood discharge that exceeds the capacity of the Citarum River. Dayeuhkolot is one of the areas that is often flooded in the Upper Citarum River Basin. The Citarum River Authority has made efforts to handle floods in Upper Citarum by constructing the Nanjung Tunnel. When floods occur, Nanjung Tunnel will function to divide the water partially into the tunnel and through the Curug Jompong. SOBEK Model was utilized to find out the effect of the Nanjung Tunnel against flood inundation in Dayeuhkolot. This flood modelling also accommodates other efforts that have been made by BBWS Citarum such as the Cieunteung Pond and Cisangkuy Floodway. A 20-year return period was used for modelling. From the results of the modelling, it was found that difference in flood inundation area with and without the Nanjung Tunnel was 12.5 Ha or 3.5 %, with the duration of the overall inundation being reduced by 4.9 hours. Nanjung Tunnel does not have a great influence on the area of inundation, but it has an effect on reducing the duration of floods that occur in Dayeuhkolot.

The aim of this study is to develop lahar hazard vulnerability as a warning system by introducing radar-rainfall observation to data mining technique of Naïve Bayes Classifier (NBC). NBC is used to estimate lahar occurrences based on the posterior probability of rainfall, topographic factor, soil moisture, and soil type as predictors. Rainfall intensity and working rainfall were obtained from a weather radar. The soil moisture is derived from SMAP satellite imagery. A river on Mount Merapi, a very active volcano in Indonesia, was selected as the target basin. Observed rainfall and recorded lahar events in Gendol River from October 2016 to February 2018 were divided into a training dataset and a testing dataset. Qualitative evaluation through visual assessment of the hazard map product reveals that the model could estimate the occurrences of lahar. The performance of the model in terms of accuracy, Brier score, and quantitative dichotomous quality indices showed a reasonable skill. The study suggests that the NBC technique is advantageous for estimating lahar occurrences that are displayed on hazard maps. This work is expected to contribute to debris flow hazard mitigation by the data mining approach in volcanic regions.

Recognizing the real-time sediment transport phenomena of rivers in the Mt. Merapi area has become an important issue, particularly in the efforts to mitigate risks of lahar flow disasters. The development of a lahar-related monitoring system in the Mt. Merapi area has currently become more challenging since contact and direct lahar flow measurement is very risky. Former techniques for lahar flow occurrences such as cable sensor and video shooting are considered good enough in terms of identifying the occurrence, but not the intensity. Furthermore, after the cable is cut, re-installation often meets its practical limit. The hydrophone measurement technique seems to be an acceptable technique subject to sufficient field calibration. This paper reports the performance of a hydrophone equipment, which can be used for monitoring bedload transport with diameters greater than 4 mm.

Pumice and scoria are pyroclastic rocks that can be found where volcanic mountains appear. In Indonesia, pumice and scoria are found in large deposits in the area of Mount Kelud at Kali Putih River in Blitar Regency, Province of East Java. Thus, it is important to evaluate their potential uses as alternative backfill materials. Standard Proctor compaction tests were conducted to determine the maximum dry density (MDD) and optimum moisture content (OMC) to evaluate their compaction properties. Constant head permeability tests were also conducted to determine the coefficients of permeability. Direct shear tests were also applied to investigate the shear strength characteristics of these materials. The results showed that the MDD values of scoria are slightly higher than pumice. The OMC values of pumice and scoria are 23% and 15.5%, respectively. The internal friction angle of pumice and scoria are higher than natural sand, which are approximately 55-64º and 46-59º respectively. Pumice and scoria with different relative densities had coefficients of permeability that ranged from 0.0003 to 0.002 cm/s and 0.001 to 0.002 cm/s respectively. Due to their mechanical properties, it can be concluded that these materials have potential as alternative backfill materials.

Dams have many benefits for living creatures. On the other hand, dam breaks may also become disasters that cause potential losses of life and property. The Cipanas Dam has been planned for construction in Sumedang, West Java, and will have a storage capacity of up to 210 million m³. The area downstream of the Cipanas Dam contains many major infrastructures such as the Cikopo-Palimanan Toll Road and Kertajati International Airport that can be impacted by dam breach floods. This study analysed Cipanas Dam breach flow using HEC-RAS 5.0.5. The simulation assumed that a dam breach occurred through piping with 5 scenarios of breach time formation. The simulation resulted in flood hydrographs and flood inundation maps of the area downstream of the dam. The findings revealed that a breach formation time of 1 hour had the greatest flood effect. The maximum flood discharge was 38, 823.3 m³s^-1 with a released water volume from the reservoir of 178, 814, 590 m³. The arrival time of the flood at the Cikopo-Palimanan Toll Road Bridge was 3 hours 45 minutes after the breach occurred, and the maximum flood depth was 15.78 m. Kertajati International Airport was not affected by the flood discharge.

Limboto is one of the watersheds in Indonesia that have suffered considerable damage. The degradation of Limboto Watershed was caused by extended land allocation for dry land agriculture that does not regard conservation practices, especially for corn as the main commodity from Gorontalo. Watershed degradation is directly proportional to an increase in critical land affected by various factors, which are land use, slope, and soil erosion. The aim of this research is to assess and to represent the spatial distribution of critical land in the Limboto Watershed based on the Directorate-General of Watershed Management and Forest Protection Regulation Number P.3/PDASHL/SET/KUM.1/7/2018 on the Technical Guidelines for the Drafting Spatial Data on Critical Land. The factors of critical land were collected and processed through a geographic information system (GIS)-based approach. The results of this study indicated that the Limboto Watershed is dominated by land of rather critical class. This provides useful information for decision makers and the local government to take appropriate land management measures in Limboto Watershed.

A combination of long-term rainfall index (LRI) and short-term rainfall index (SRI) is commonly used as an indicator for estimating whether a series of rainfalls is likely or unlikely to cause landslides or lahar flows. The LRI represents the condition of soil structure instability. The SRI represents the condition of soil surface instability. A critical line can be drawn separating zones of occurring and non-occurring landslides or lahar floods. An occurrence of series of rainfalls can be monitored by drawing a snake line representing the progression of LRI-SRI values. By selecting an appropriate definition of LRI and SRI indices, a continuous snake-line can be developed for monitoring warning conditions of progressing rainfall events. Several existing definitions of LRI vs. SRI such as cumulative rainfall vs. hourly rainfall, working rainfall vs. hourly rainfall, and working rainfall with long half-life vs. working rainfall with short half-life were reviewed in terms of their effectiveness in delivering warning and practicability in drawing and reading the snake-line. A procedure for accommodating snake-line drawings of several definitions was established. The procedure was tested by several serial rainfall events and has shown good capability in facilitating monitoring activities for landslides or flood warnings.

Sidrap Regency is one of the special economic zones in South Sulawesi. It has been growing rapidly from rural land to an industrial city since mid-2005. With the process of urbanization, flooding has become a threat to the security of the city area. In this study, Bila River basin in Sidrap Region was selected to investigate the effect of urbanization on surface runoff and peak discharge. The methodology involved hydrology database building, a detailed Digital Elevation Model (DEM), a land use cover and a soil map of the basin. With all these data, the SWAT model (Soil and Water Assessment Tool) was used to predict discharge values. These discharge values were used, along with the DEM, to predict flood hazard areas in the Bila river basin floodplains. This procedure was made using the HEC-RAS model (Hydrological Engineering Centre-River Analysis System). The results of SWAT Model showed that changes in land use had a significant impact on increasing river discharge. The results of HEC-RAS show that with a planned flood of a return period of 10 years (840 m³/s) can cause flooding on Bila River, because the existing capacity for this river is 412.70 m³/s. The study shows the 2D capability of the new HEC-RAS 5 for flood inundation mapping and management studies.

The environment is a combination of two things: resources and hazards. One of the hazards that is a result of environmental changes is the occurrence of natural disasters. Floods are one of the disasters that is feared by people in society. Negative impact of floods is the affected quality of raw water in the flooded area. Polluted water will certainly have a negative impact on the health of the human body. From the explanation above, this article analyzes changes in water quality that occur in flood-affected areas. The utilized method is the empirical legal method, by describing the state of the research subject based on existing conditions and in relation to existing legal regulations. The results obtained from this study showed that irresponsible individuals had committed many violations by building factories on the riverbanks. This causes the river water to overflow and damage buildings, dikes, settlements, and so on. The advice that can be given is to give strict sanctions to people who intentionally or unintentionally violate legal regulations, as well as to build cooperation between society and the government to conserve nature and foster self-awareness to preserve the environment.

The aim of this study is to create a scenario for investigating the factors that affect the vegetation density and to design the formulation of vegetation density as one of the factors on the revised universal soil loss equation. The methodology consists of 1) measuring vegetation density in 10 watersheds/sub-watersheds by using satellite imagery and field observation; 2) studying the factors that influence vegetation density based on literature review; 3) determining the dominant factors that influence vegetation density based on statistical analysis; 4) formulating vegetation density based on the statistical analysis results; and 5) validating the formulation of vegetation density using the universal soil loss equation as the control. The result is expected to allow for prediction of the effect of reforestation on decreasing soil erosion.

I Gusti Ngurah Rai Airport is an international airport in the Province of Bali with high traffic. The government of the province encouraged the airport services company to increase the airport's capacity by expanding the aircraft apron. To initiate this project, land reclamation had been carried out on the west side of the existing apron. However, a sea wall was used for protecting the reclamation area from attack by waves. This case study of the reclamation area is intended to investigate its geotechnical aspect, in which the potential of liquefaction is necessary to be evaluated. The liquefaction is quantified by referring to CPT (cone penetration test) and SPT (standard penetration test) data. Analysis results of the reclamation area at location 1 (CPT testing) and location 2 (SPT testing) showed occurrences of the liquefaction hazard, where the FS (safety factor) was found to be less than 1. This means that soil improvements, such as utilizing a vibro-compaction method, are required. The steps of the vibration method are considered as the simplest method, particularly for compaction of sand material in the reclamation area. The criteria evaluation standard for the compaction is Dr (relative density) of greater than or equal to 70%.