Water quality monitoring of welang river basin

The Welang watershed, located in Malang Regency and Pasuruan Regency, has diverse human activities that can affect watershed hydrology, one of which is related to water quality. The purpose of this research is to determine the current water quality of the Welang watershed. This research was conducted in March 2023 - June 2023, which was conducted using random purposive samples with parameters of sunlight intensity, humidity, air temperature, water temperature, pH, TDS, brightness, chlorine, bromine, lead, nitrate, nitrite, fluoride, iodine, cyanuric acid, carbonate root, and total alkalinity. From this study, it was obtained that the upstream part of the Welang River on the Arjuno side and Bromo side contained Chlorine (Cl), Bromine (Br), Iron (Fe), Lead (Pb), Nitrate (NO3-), Nitrite (NO2-), Fluoride (F-), and Carbonate Root (CO3 2–). Meanwhile, the middle part of the Welang River dominantly has the same content, but no Iron (Fe) was found but instead Cyanuric Acid C3N3(OH)3. Meanwhile, the downstream part of the Welang River contained Chlorine (Cl), Copper (Cu), Lead (Pb), and Fluoride (F-).


Introduction
A river basin (Watershed) is a land area that is a unit with rivers and tributaries that functions to store, accommodate, and channel water resulting from rainfall to the sea or lake naturally.Indonesia has many watersheds.One of them is the Welang Watershed [1].The Welang watershed is one of the large rivers and one of the main watersheds in East [12].The watershed Welang is one of the rivers in East Java that passes through 3 administrative regions, namely Malang Regency, Pasuruan Regency, and Pasuruan City.The Welang watershed is 40.6 km long.The upstream and downstream watershed area is 498.03 km 2 [1].
The downstream part of the Welang River crosses Pasuruan City and Regency, the middle and upstream parts cross Pasuruan Regency, and the upstream part crosses part of Malang Regency, precisely in Lawang District.The upstream part of the Welang River is a hilly or mountainous area in the Mount Arjuno and Mount Bromo areas.The downstream part of the Welang River empties into Kraton District, north coast of Java Island, Madura Strait [12].
IOP Publishing doi:10.1088/1755-1315/1312/1/012017 2 With this area and length, it creates a watershed Welang has many benefits for the local community.Among them are daily activities such as bathing, washing, irrigation, and other needs.These many benefits mean that the Welang watershed is often faced with problems such as flooding, environmental sanitation problems, and damage to infrastructure and rice fields [12].The decline in land quality in the Welang Watershed is directly proportional to the decline in water quality in the Welang River due to rubbish, domestic waste, agricultural waste, and industrial waste.The majority of community activities along the Welang River will affect the quality of river water [12].Based on this, measuring river water quality in the Welang watershed is necessary.So this research aims to determine the current water quality of the Welang Watershed.

Tools and materials
The equipment needed in this research is a 15in1 water test strip to measure water quality, a pH meter to measure the pH value, a Total Dissolved Solids (TDS) meter to measure the TDS value in the water content, a thermometer to measure the temperature value in the water, an anemometer used to measure air temperature and lux meters are used to measure light intensity and air humidity [4].

Research methods
This research used a random purposive sample.The water quality parameters measured are hardness, chlorine, bromine, iron, copper, lead, nitrate, nitrite, fluoride, iodine, cyanuric acid, carbonate root, and total alkalinity.Meanwhile, the environmental parameters measured in this research are sunlight intensity, humidity, air temperature, and water temperature.

Result and Discussions
Welang river basin, devide based on upstream, middle and downstream.In general, the Welang river basin, with coordinates from 112°36 E to 1135°3 E and 7°53 S to 7°35 S with an altitude value of 0 -3,233 m (Figure 2).Welang watershed (DAS) based on Keppres 12/2012 (Presidential Decree) is included in the Welang Rejoso River Basin and administratively this river is a cross river between Pasuruan City, Pasuruan Regency and Malang Regency so that the management of the Welang river becomes the authority of the Government of East Java Province.In this research there are 19 points number of water sampling.The upstream divided into two parts with the flow from Mount Arjuna and from Mount Bromo (Figure 3).The upstream is number 1-12, from Arjuno side is point 1-6 and Bromo side is points 7-12.The middle of Welang river is number 13-16, and the downstream is number 17-19.Tabel 1.The condition of water quality from Welang shows indications of being polluted so that if the water is stagnant, the Welang river will be put into ground water then it must be treated first [19].Therefore this research was conducted to monitoring of Welang water quality.onsand subsubsections.

Environmental Quality Parameter
Environmental quality is one of the factors that affect water quality with several sampling points in the Welang watershed, including based on upstream, middle and downstream areas.The upstream part is at point number 1-12 which is divided into two parts with the flow from Mount Arjuna from Mount Bromo, part of the Welang River.While the middle part of the Welan gada River is at points 13-16, and the downstream of the Welang River is number 17-19.The measured environmental quality includes water color, light intensity, air temperature, humidity, water temperature.Based on the measurement results, it is known that the quality of water color from upstream to downstream has decreased from clear to cloudy.While the light intensity from upstream to downstream has increased in intensity because generally the upstream part of the river is in a highland area full of trees, while the downstream part of the river towards the estuary leads to the coastal sea area.Furthermore, the air temperature in the study area has a range of 25.95 ˚C to 41.6 ˚C from upstream to downstream.Then for air humidity also has an unstable value with a range of 38 to 78.
Air temperature is one of the factors that affect water temperature and directly affects the physical and chemical properties of waters, the color of water whose quality decreases from upstream and downstream shows that water quality in the middle to downstream has low oxygen levels due to the high amount of plotan in water [3].Light intensity affects water temperature, high light intensity affects the increase in water temperature [8].While air humidity is the amount of water vapor contained in the air, meaning the more humid the air in the area [18].

Water Quality Parameter
Water sampling to determine water quality was carried out by dividing it based on the upstream, middle and downstream areas of the Welang River.Sampling locations for the upstream Welang River are at points number 1-12 which are divided into two sections, numbers 1-6 upstream with water flow originating from Mount Arjuna, while numbers 7-12 upstream with flow originating from Mount Bromo, part of the Welang River.middle numbers 13-16, and the downstream Welang River at numbers 17-19.The results of water quality sampling can be seen in Table 3.
Based on Table 3 the results of each parameter, it was found that the upstream Welang River area had a pH of 6,83-7,5, TDS 53.5 mg/L -152 mg/L, water temperature 24,35°C-29,7°C, hardness 100, free chlorine 0-0.5, free bromine 0-1, total chlorine 0.5, iron 0-0.5, copper 0, lead 20-50, nitrate 100, nitrite 20, fluoride 25, iodine 0, Cyanuric Acid 0, carbonate root 0-20, and total alkalinity 80-120.For results in the middle part of the Welang River, pH 6.75-7.76,TDS 127.5 mg/L -208,5 mg/L, water temperature 28,5°C-30,01°C, hardness 100, free chlorine 0-1, free bromine 0-1, total chlorine 0,5, iron 0, copper 0-5, lead 20-50, nitrate 25-50 nitrite 5-10, fluoride 25, iodine 0, Cyanuric Acid 0, carbonate root 20, and total alkalinity 80-160.And for the results of the downstream Welang River area, pH 8-8,3, TDS 214 mg/L -1000 mg/L, water temperature 31,5°C-34,6°C, hardness 100.The pH results in the Welang River between downstream and downstream are 6.83-8.3,which is still classified as normal water pH conditions.If the pH of water decreases until it becomes acidic or increases until it becomes alkaline, it can disrupt the environmental balance in the water.The pH concentration affects the fertility level of waters because it affects the life of microorganisms.Acidic waters tend to cause death in fish, as does pH that is too alkaline [20].The temperature ranges from 24,35°C-34,6°C which is still considered normal, this is because if the temperature exceeds 35°C it 6 can cause oxygen levels to decrease and affect all organisms in the water.The higher the pool temperature, the faster the reaction of ammonium to ammonia [15].Ammonia is more toxic than ammonium.Another thing that can cause changes in temperature in a body of water is due to the influence of the absorption and release of heat from the hot sun.Changing temperatures can affect the growth of phytoplankton and organisms in these waters.Furthermore, the TDS parameter has a result of 53.5 -1000 mg/L, with the lowest TDS found in the upstream Welang area and the highest TDS found in the downstream Welang, this is because it is located in an estuary, apart from the downstream area of the estuary, other samples were taken which had results.TDS is 234 mg/L and this TDS is higher than at other collection locations.If high levels of TDS are not managed and treated, they can pollute water bodies and can kill aquatic life.
The results of the chemical parameters obtained from the water test strip are : The Welang River upstream on the Arjuno side and Bromo side contains Chlorine (Cl), Bromine (Br), Iron (Fe), Lead (Pb), Nitrate (NO3-), Nitrite (NO2-), Fluoride (F-), and Carbonate Root (CO3 2-), in the middle part of the Welang River, predominantly has the same content as upstream but no Iron (Fe) was found, and Cyanuric Acid C₃N₃(OH)₃ was found.Meanwhile, in the lower reaches of the Welang River, Chlorine (Cl), Copper (Cu), Lead (Pb) and Fluoride (F-) were found.The highest parameters related to the heavy metals Chlorine (Cl) and Bromine (Br) were found in the middle Welang River area with a value of 1, Iron (Fe) was highest in the upstream Welang River area with a value of 5, Copper (Cu) was highest in the upstream Welang River area with value 5, and Lead (Pb) is highest in the upper and middle reaches of the Welang River with a value of 50.Heavy metals in waters have an impact on aquatic organisms and humans.Heavy metals that enter the human body are also dangerous for health.Heavy metals are one of the toxic pollutants that can cause death (lethal) or non-death (sub-lethal) such as disrupting the growth, behavior and morphological characteristics of various aquatic organisms [5].The impacts resulting from the presence of heavy metals in waters depend on the presence of metals in water and sediment, their toxic power and their concentration in the environment.If heavy metals enter the bodies of living creatures, they will experience bioconcentration, bioaccumulation and biomagnification [6].Heavy metals can block the work of enzymes so that the body's metabolism is disrupted, causing cancer and mutation, such as several heavy metals which are very dangerous for humans, including lead, copper, mercury, cadmium and chrome [11].
The highest Nitrate and Nitrite parameters are found in the Upper Welang River with levels of 100 and 20.The high Nitrate and Nitrite content can be caused by agricultural and plantation activities which still use a lot of chemicals in their management such as chemical fertilizers and pesticides.The abiotic environment can be polluted by the transformation products of nitrogen such as nitrate, nitrite and ammonia [20].Nitrate is a nutrient for the growth of aquatic plants and algae, causing uncontrolled growth of aquatic flora, while nitrite is a toxic compound that can kill aquatic organisms [11].
High nitrogen concentrations can cause excessive phytoplankton growth or eutrophication and can cause water pollution [17].The highest Fluoride results were found in the Upper and Middle Welang River with levels of 25, while Iodine was not found in the entire Welang River area.Too much fluoride in waters can actually be toxic to marine biotaand increases in fluoride are usually caused by human activities such as industrial activities, water fluoridation, and waste disposal [4].Cyanuric Acid is only found in the middle part of the Welang River with a level of 30, while carbonate root is found in the upper and middle Welang River with a level of 20.And the highest total alkalinity parameter is found in the upper Welang River with a level of 180.Meanwhile, hardness in the entire Welang River has a level the same, namely 100.Hardness is one of the chemical parameters of water which is caused by the presence of a fairly high content of and metal ions.The maximum hardness limit in clean water is 500 mg/L, apart from that hardness can also be caused by other metal ions as well as bicarbonate and sulfate salts.

Conclusions
Based on the sampling data, the Welang River area was found to have the highest water quality parameters from upstream to downstream is Chlorine (Cl) 1, Bromine (Br) 1, Iron (Fe) 5, Lead (Pb)

Figure 1 .
Figure 1.Welang River water sampling map This research was carried out from March to June 2023.Water quality measurements were carried out from the upstream to downstream areas of the Welang watershed.There are 19 sampling points.Among them are Points 1-6, the upstream areas on the Arjuno side.Points 7-12 are the upstream area on the Bromo side.Points 13-16 are the middle part.Points 17-19 are downstream.

Table 1 .
The Location of point/number sampling.

Table 2 .
Environmental Parameter

Table 3 .
Water Quality Results for the Upper, Middle and Downstream Welang Watershed.