Lake management in ASEAN countries: issues and challenges

As human populations grow, societal demands led to aquatic ecosystems degradation and vulnerabilities. In this paper, we identified several drivers to the impairment of water bodies in ASEAN, which are partly influenced by socio-economic activities of the nations, the morphometry, and watershed of the selected lake basins. There are barriers in managing these ecosystems, including fragmented management and administration, a lack of intersectoral coordination and governance, insufficient enforcement measures, and limited resources. A multi-dimensional approach is required to achieve a balance between environment, economy, and social needs, so that a resilience water body could be conserved. To achieve this, it is imperative and timely for the governments to include the inland waters as a prominent resource in the national water agenda, considering the present Decade for Ecosystem Restoration.


Introduction
ASEAN nations are not only rich in biodiversity, but also diverse in inland water ecosystems that hold ecological and cultural importance, playing significant social and economic roles.Despite their importance in resource-provisioning services, lakes and reservoirs are threatened by multiple anthropogenic pressures, resulting in various ecological issues that demand both local and global attention.Thus, unique complex issues facing the nations should be addressed accordingly, making it timely to establish international networks focusing on policies, scientific data collection, and sharing of crucial information.This inspired the establishment of the Southeast Asian Limnological Network or SEALNet during the 16th World Lake Conference held in Bali, Indonesia from November 7th to 11th, 2016.The focal aims of SEALNet are to forge a mechanism for information exchange on lakes and 1313 (2024) 012017 IOP Publishing doi:10.1088/1755-1315/1313/1/012017 2 other inland waters, facilitate collaborative research on common needs, aid cross-visits of experts and students, and to strengthen policies on conservation and management through evidence-based interdisciplinary research.Thus, under the theme of lake ecosystem and management, we gathered information on the issues and challenges of inland water management, focusing on selected water bodies from each core member country of SEALNet; Indonesia, Malaysia, Thailand, Philippines, and Laos (Figure 1).Understanding the condition of these aquatic ecosystems is critical for the development of effective plans to maintain, manage, and restore them.The deterioration of aquatic ecosystem functions and services worldwide has accelerated due to changes in climate and land-use pattern.Thus, by having collaborative works among ASEAN and other international prominent scientists and lake basin managers, these critical issues of ecosystem deterioration can be collectively addressed, and cohesive management strategies can be proposed.
1.1.General background of selected water bodies 1.1.1.Indonesia; Batur Lake -Indonesia is blessed with a large number of natural lakes that have been formed by tectonic and volcanic activities.Among these fascinating ancient lakes, Batur Lake is notable for its unique characteristics.Located in Kintamani, Bali, Indonesia, Lake Batur is one of 15 national priority lakes in the country.It is a crater lake inside of the caldera of an active volcano, Mount Batur, located along the Ring of Fire of volcanic activity and at an elevation of 1,050 m above sea level.The surface area of the lake is 16.05 km 2 , with a water volume of 815.38 million m 3 and an average depth of 50.8 m.Batur Lake water is sourced from rainwater and seepage from the surrounding mountains with a catchment area of 105.35 km 2 [1].

Malaysia; Temengor Reservoir -Temengor
Reservoir is located at the highest elevation of the Perak River basin, in the northern part of Peninsular Malaysia.With a surface area of 15,200 ha, mean depth of 40 m and storage capacity of up to 6.05 × 109 m 3 [2], this reservoir ranks as the second largest man-made lake on the peninsula.Constructed mainly for hydroelectric power generation, Temengor Reservoir is dendritic in shape and surrounded by forest reserves which function as water catchment areas [3].
1.1.3.Thailand; Songkhla Lake -Situated in the southern region of Thailand, Songkhla Lake is the largest lagoon system and the sole lake basin within the country.This expansive lake spans an area measuring 1,042 km 2 [4], encompassing diverse landscapes ranging from tropical rainforests in the upstream watershed to a complex water quality regime comprising freshwater bodies, brackish and saline waters.Songkhla Lake are influenced by various factors such as tidal patterns that affect the sea water intrusion from the Gulf of Thailand, as well as runoff originating during monsoon seasons through twelve major rivers and numerous streams that flow into it.These geographic features contribute significantly to the sustenance of aquatic life within this natural habitat while also shaping its overall biodiversity.
1.1.4.Philippines; Laguna Lake -Laguna Lake, also known as Laguna de Bay in the Philippines is the largest and most socio-economically significant lake among the more than 221 natural lakes in the country.The lake's surface area is 900 km 2 with a watershed of 2,980 km 2 that cradles 6 provinces including Metro Manila.Despite its large size, the lake is relatively shallow with an average depth of 2.5 m and a water volume of 2.25 x 109 m 3 .The high surface area to volume ratio accounts for the perennial turbidity of the lake.There are 24 major tributary rivers with only one outlet, the Pasig River, which connects it to Manila Bay.The lake periodically receives saline water due to backflow from the Pasig River, thus the lake is not a purely freshwater lake.
1.1.5.Laos; Beung Kiat Ngong Wetlands -Beung Kiat Ngong Wetlands is one of the two wetland areas in Lao PDR that was declared a Ramsar site after Lao PDR became a party to the Ramsar Convention in 2010.Covering an area of 2,360 ha, this wetland is located approximately 56 km south of the provincial capital, Pakse.The southern parts of the wetland, as well as most of the village of Ban Kiat Ngong, are located within the Xe Pian National Protected Area (NPA) [5].At a broader regional scale, the Beung Kiat Ngong wetland is encompassed by the Indo-Burma Biodiversity Hotspot or the Central Indochina area (tropical lowland plain) [6].

Importance of lakes
In ASEAN countries, inland water systems which include lakes, reservoirs and wetlands are important water resources that provide various ecological functions and socio-economic benefits.They harbour a high diversity of potentially endemic, rare, and endangered species of flora and fauna.Generally, the selected water bodies in this review share the similar ecological services, which are described under specific sub-headings.

Fisheries: capture and culture
One of the important resource-provisioning services provided by lakes is capture fisheries and aquaculture.Lakes serve as a significant resource for various species of fish, many of which are endemic and have commercial value, while aquaculture is mostly focused on the introduced species.
In Batur Lake, the fish diversity comprises two families: the Cichlidae (Oreochromis niloticus and Oreochromis mossambicus) and Cyprinidae (Cyprinus carpio and Rasbora lateristriata) [7].Lake Batur is extensively utilized by the community for aquaculture using floating net cages, with a primary focus on tilapia Oreochromis niloticus [8].
Temengor Reservoir and its tributaries have abundant ichthyofaunal composition including two endangered fish species; mahseer Tor tambroides and Malaysian carp Probarbus jullieni, alongside the queen danio Danio regina, a sought-after ornamental species [9,10,11].Furthermore, the reservoir hosts commercially significant species like carp Hampala macrolepidota and snakehead Channa micropeltes, showing the potential for commercial fishing [12].A major tilapia aquaculture was established within the Aquaculture Industrial Zone (AIZ) in 2008 covering a water body of 100 ha [13].
The fishing industry in Songkhla Lake is vital for the local economy.As a result, the local government has proactively taken several steps to manage fish stocks sustainably and promote responsible fishing practices.The 2023-2027 Development Plan for Songkhla Province is formulated towards enhancing aquatic resources and establishing fish shelters.This effort aims to achieve a balance between fishing productivity and biodiversity conservation, ensuring the sustainable income of local fishermen and supporting the community's economy.
Laguna Lake was traditionally used for fishing, with 31 fish species recorded.The most dominant and economically significant species were silver therapon Therapon plumbeus and white goby Glossogobius giurus.In addition, other commercially important fishes include, Ophicephalus striatus, Chanos chanos, Clarias sp., Arius manillensis, Tilapia mossambica, T. nilotica, Cyprinus carpio and Trichogaster sp.However, in the early 1970s, the introduction of aquaculture brought significant changes to its fishery.Studies have shown that the lake could naturally supply the food needed for cultured fish, initially milkfish Chanos chanos.In the early 1980s, Tilapia sp. and big head carp Aristichthys sp. were introduced for culture, leading to extensive aquaculture.This attracted numerous entrepreneurs, resulting in nearly two-thirds of the lake being occupied by fish pens and cages.The critical situation was addressed by the Laguna Lake Development Authority by implementing a Zoning and Management Plan (ZOMAP) in 1983 which is periodically revised based on the carrying capacity of the lake for aquaculture.The latest revision was in 2019 wherein the allowable area for aquaculture was set at 9,200 hectares of which 60 % (5,520 ha.) is allocated for individual fisherman and cooperatives and 40 % (3,680 ha.) for business persons.
Beung Kiat Ngong is important to the community of more than 8 core villages and 11 additional villages.The inland fisheries are generally managed as a common resource, allowing people to catch numerous tons of fish yearly and serving as breeding habitat for various fish and aquatic species.

Habitat for wildlife (biodiversity)
Apart from fisheries, the lake hosts several important biodiversity.Batur Lake harbors various aquatic species, including families of aquatic macrophytes observed on the lake surface.Despite the endemism of Najas marina var.zollingeri to Batur Lake, references on this species remain scarce [14].Phytoplankton and zooplankton are also diverse in this lake.Additionally, Thallophyta, which comprise of lichens, fungi and algae is also recorded in this lake.
Temengor Reservoir also encompasses a variety of aquatic insects, macrophytes, phytoplankton, zooplankton and more.Apparently, the presence of three aquatic insect orders, namely Ephemeroptera, Plecoptera, and Trichoptera (collectively known as EPT), are also recorded.These orders serve as indicators of clean water bodies [15].In addition, Chironomid larvae (non-biting midges) and aquatic beetles, which function as indicators for water quality (i.e., physico-chemical and biological) [16] are also recorded in the Temengor Reservoir.
Laguna Lake is endowed with rich natural resources, serving as a habitat for a variety of organisms that contribute to its biodiversity pool.Besides phytoplankton, zooplankton, and macrophytes, the lake supports other thriving organisms of various mollusks, crustaceans, and birds that rely on the lake's resources.The freshwater prawn Macrobrachium sp. is also harvested commercially.A wide variety of waterfowl observed, including common species such as Ixobrychus sinensis, I. cinnamomeus, Ardea cinerea, Rallus mirificus (an endemic Philippines species), Porphyrio porphynio, Fulica ama, Himantopus himantopus and Sterna albitrons [17].
The diverse habitats within the Songkhla Lake Basin are hotspots of biodiversity.The lake hosts a wide range of flora and fauna, including organisms adapted to saline waters near the sea, tolerant brackish water species, and freshwater dwellers.Although some species may be scarce at times, the overall diversity remains significant.Moreover, the basin serves as an important feeding ground for certain plankton that migrate from the sea driven by tidal flows.Additionally, some shrimp species only seasonally gravitate towards the lake to meet their dietary needs.
Beung Kiat Ngong wetlands is an important wetland consisting of swamps, lakes, peatlands, and marshes.The edges of the wetland are forested and are surrounded by large trees, including species typically found in the south and east of Lao PDR.The forest thrives due to the quality of the soil and the abundance of water.Seasonal and perennial flooded grasses are also recorded here.The Beung Kiat Ngong Wetlands represent one of the peatlands present in Lao PDR.

Hydropower generation
Temengor Reservoir was initially used to generate hydroelectric power in 1978 and as a source for domestic water in 1999.The construction of water dam has changed the hilltops into islands with different shapes and sizes [3].Characterized by a relatively dendritic shape and steeper cliffs, the Temengor Reservoir features a dam built across the rivers in the highlands, covering the lower-order streams [18].
In Laguna Lake, hydropower generation commenced in 1982 with the operation of the Kalayaan Pumped Storage Power Plant.This power plant is the first and only pumped storage facility in the Philippines, situated in the eastern bay of the lake.During the low electricity demand at night, water from the lake is pumped into the Caliraya Reservoir.In contrast, during the high demand at daytime, the plant generates electricity and the water is released back to the lake.The complex has a total capacity of 736 megawatts [19].

Water regulation
The Temengor Reservoir hydrological system is critical for regulating water levels in both the reservoir and the surrounding areas.It is the largest raw water storage facility that generates hydroelectric power and distributes a clean water supply to adjacent human settlements for domestic usage and irrigation for agriculture.Additionally, it plays an important role in flood mitigation in the region by controlling the dam gate, where the gate can be lifted to release excess water into the downstream reservoir in order to maintain the optimal water level for the Temengor Reservoir [20,21].
Flood waters from Metro Manila are being diverted to Laguna Lake through the Manggahan Floodway; a man-made canal constructed in the 1980's.However, this flood water diversion has significant effect on the coastal areas especially in Rizal Province.During extreme typhoon events, it usually takes months for the lake water level to recede thus, exposing the coastal communities to health and economic risks.The hydrological system of the Songkhla Lake plays an essential role in regulating water levels within both the lake itself and its surrounding region.Serving as a natural reservoir, it aids in flood control during monsoon seasons by receiving runoff from twelve major rivers and various streams flowing into it.Additionally, the system contributes to groundwater recharge through infiltration processes, ensuring adequate supplies for agricultural irrigation and domestic use.

Eco-tourism
Batur Lake is a renowned tourist destination in Bali.Its location in the highlands on the slopes of Mount Batur contributes to its uniqueness, and it is recognized by UNESCO as a Global Geopark Network area.Batur Lake offers chilly mountain weather and lacks modern vibes, except for a few cafes overlooking the lake.Several ancient villages have been thriving for centuries around Batur shore; with the most notable being the Trunyan village, known for its unique burial practices.
Apart from the Temegor Reservoir itself that offers a scenic and picturesque view, the Belum-Temengor Forest Reserve that lies within the lake is also a popular tourist hotspot.Its ecotourism governance system resembles the area's protected status.The Ministry of Tourism and Culture is responsible for the general planning and development of ecotourism, while other state agencies are responsible specifically for ecotourism activities.The only access to Belum-Temengor tourism sites is by boat; either from Banding Island's public jetty or the resorts' private jetties.
Songkhla Lake is a major tourism attraction, famous for its scenic beauty, rich biodiversity, and for recreational opportunities, which collectively draw tourists from all around the world.The recent implementation of the 5-Year Strategic Plan for the Special Development Area of the Songkhla Lake Basin 2023 -2027 aims to develop tourism through a participatory approach.The plan seeks to reduce income inequalities, promote sustainable tourism practices, create globally recognized sustainable standards, and facilitate cooperation amongst all sectors.This plan endorses the conservation of cultural diversity while improving income distribution to local communities.
Beung Kiat Ngong Wetlands are well-known tourism destinations in Champassak Province.Blooming tourism activities in the Kiat Ngong Village provide another stable income to the villagers.They had the opportunity to participate in various services such as elephant riding, guiding tours, operating guesthouse and home-stay services, and selling handicrafts and local products to tourists.In the wetlands, tourism is organized by the local community through the "village information office" which includes a restaurant and a souvenir shop [22].
However, the full potential of Laguna Lake, for recreation and nature appreciation has not been given much focus.This inadequate attention could be due to the observed environmental degradation in some parts of the lake, especially in areas closer to Metropolitan Manila.

Other ecosystem services
Inland water bodies also provide important ecosystem services.Functioning as natural regulators of river flow, these water bodies trap sediments and nutrients carried by the rivers and streams that flow into them.The vegetation along the shorelines, known as riparian vegetation, helps to stabilize the sediments.Unfortunately, the significant role of the lake as a natural purification system remains unknown by the community, thus, it is not appreciated and treasured, especially by those that depend on the lake for their livelihood.Eventually, these pollutants accumulate and gradually stress the lakes in numerous ways, causing them to lose their ability to be self-sustaining.Over time, this will cause an impairment of lake quality for other uses.There is a need to educate the public about this very important ecological function to prevent the excessive capacity of the lake.

Issues related to lake ecosystem health
There are many stressors that affect aquatic ecosystem health, including population growth, resource exploitation, urban and municipal development, climate change, etc.These developments have resulted in adverse changes in the hydrology and ecology of inland water ecosystems [23].We identified several prevalent issues and degrading factors that affect the selected water bodies in this review, which are highlighted under their respective sub-headings.

Sedimentation
Deforestation in the Batur Lake catchment area causes a decrease in the infiltration rate of rainwater, an increase in surface runoff, and erosion which carries dissolved material and precipitates sedimentary material into the lake.Batur Lake sediment calculations from 1975 to 2012 showed that, the sedimentation volume was 124.71 million m 3 , the sedimentation thickness was 7.80 m, and the sedimentation rate was 0.21 m/year.This has led to a decrease in water depth for 37 years of 7.8 m and a decrease in water volume of 124.71 m 3 [24].
Temengor Reservoir is connected to several rivers with different characteristics, particularly in terms of human activity and sedimentation processes [25].These rivers face threats and are influenced by various natural and human activities.During the period of heavy rains, the bare soil resulting from logging activities contributes to increased turbidity in the lake due to sediment re-suspension [26].
The major contributor to sediment loading in the Laguna Lake was attributed to the accelerated soil erosion due to land conversion and a rapid decline in forest cover.The bathymetry analysis conducted by the LLDA showed that the average depth in 1997 was 2.54 m while in 2014, the average depth had decreased to 2.43 m.
Songkhla Lake is facing increased shoaling primarily due to human activities, resulting in sediment deposition from the surrounding areas.The three main sources include: 1) sediment from the seashore, influenced by tidal fluctuations; 2) soil run-off carried by rivers during the rainy season, especially from deforested areas used for agriculture or mining; and 3) plant and animal wastes, particularly in the nutrient-rich and shallow areas.Although each source contributes to the overall problem, addressing these issues collectively is important to mitigate further damage and preserve the ecological balance of this crucial water body.

Pollution
In Batur Lake, several anthropogenic activities have been identified as potentially contributing to organic waste, including residential areas, aquaculture and agriculture, tourism, and religious ritual activities [24].The latest condition showed that several water quality parameters have exceeded the permissible level [27,28,29].Hence, based on the Regulation of Bali Governor No. 16 of 2016, the water of Lake Batur is not potable; it is only suitable for fisheries and agriculture [28].
As Temengor Reservoir is a popular destination for ecotourism and recreational activities, boating has become prevalent activities.However, these activities could pollute the water body, including the oils spill and waste discharge from the boats.Some of the boathouses are equipped with septic tanks to collect waste, while others lack suitable sewage treatment and disposal facilities.The absence of proper maintenance and inadequate septic tank systems can lead to unsanitary conditions, posing risks to both human health and the environment.A significant concern arising from this improper handling is the presence of bacterial growth, such as Escherichia coli.Therefore, implementing a proper sewerage treatment system with disinfection processes is crucial to address these issues.This will ensure the discharge of high-quality effluent, eliminating bacterial growth and preserving the water quality of the lake.
In Laguna Lake, the most recent water quality assessment conducted by LLDA showed that the concentration of inorganic phosphate has exceeded the water quality guideline for Class C water of 0.025 mg/L [30].This trend has been observed in previous years, as reported in the first Laguna de Bay Ecosystem Health Card Report published in 2015.This initial report indicated a low water quality rating due to the high concentration of inorganic phosphate.Untreated domestic wastes pose a serious concern in the region.Sewage treatment facilities are existed only in the service areas of the water concessionaires and in some recently developed gated residential houses.In most communities, primary treatment is commonly involves using septic tanks.However, in some areas, domestic wastes are directly discharged into waterways that eventually drain into the lake.Human activities had a detrimental impact on the ecosystem of Songkhla Lake.A recent study analyzed core samples from the lake sediment, spanning over 55 years, and revealed three distinct periods of trace metal influxes attributed to human influences [31].Additionally, the COVID-19 pandemic brought forth new concerns as another study discovered the presence of microplastics in fish and shrimp stomachs within Songkhla Lake [32].Notably, fibre microplastics were found, which could be attributed to increased laundering activities during lockdown measures.Therefore, it is evident that changing lifestyles and daily habits have led to evolving patterns and emerging risks affecting the water quality of Songkhla Lake.

Eutrophication
Several studies revealed that Batur Lake experienced eutrophication based on the tropic level measured by water transparency, total nitrogen, total phosphorus, and chlorophyll-a parameters [33,34].Eutrophication is also caused by an excess of nutrients from fish floating cages in the vicinity of the lake and surrounding agricultural areas [24].
In Temengor Reservoir, water within a 3km radius from fish cage areas, was initially mesotrophic [35,36].However, recent findings showed a decrease in water quality in the same area, now classified as eutrophic, indicating a noticeable deterioration in water conditions [21].Despite the eutrophic state of the water column, the studies conducted did not report any occurrence of algal blooms [21,36].Nevertheless, the large surface area, depth and water level of Temengor Reservoir have mitigated the impacts of eutrophication to some extent.
Laguna Lake is a eutrophic lake, and can be hypereutrophic at certain times of the year, with periodic occurrence of algal blooms, mostly by Microcystis sp.Fishkill episode is common which not only affected the aquaculture businessmen but also the fishermen.Another manifestation of a eutrophic lake is the infestation of water hyacinth.This phenomenon is persistent, to the extent that a lakeshore town has declared a "State of Calamity" due to massive growth of water hyacinth.This infestation not only affected the livelihood of fishermen, but has also blocked the navigational routes, isolated communities, and the closure of fishing ports.
In Songkhla Lake, the excessive enrichment of water bodies with nutrients, is another major issue reported [37].This process is mainly driven by factors such as agricultural runoff, domestic sewage, and industrial discharges, which introduce high levels of nutrients such as nitrogen and phosphorus into the lake.As a result, there is an overgrowth of algae and aquatic plants, leading to water quality deterioration and oxygen depletion.

Invasive species
Several introduced species have been recorded in Temengor Reservoir, including snakeskin gourami Trichogaster pectoralis, peacock bass Cichla ocellaris and tilapia Oreochromis niloticus.Although T. pectoralis has not threatened the native fish species, the other two species are considered invasive and pose a threat to the river ecosystem and its resources.It is crucial to implement effective monitoring and enforcement measures to control the population of these species.Additionally, regular inspections should be conducted on the species cultured despite on a small-scale, to prevent any further negative impacts on the ecosystem.
In Laguna Lake, there were reports on invasive alien species (IAS) introduction into the lake, either accidentally or intentionally.The most recent IAS are janitor fish Pterygoplichthys sp. and clown knifefish Chitala ornata.The infestation in the lake was severe that an inter-agency Task Force, was created by the Department of Agriculture to control the population of these invasive species and to find means to use the invasives for economic gains.Among the components of the Task Force's program is to encourage fishermen to catch these invasive fish for monetary incentive and develop products from them.At present, these invasive species are being sold for certain food products and sauces.

Biodiversity loss
To date, no documentations on diversity loss have been reported in Temengor Reservoir.However, several freshwater fish species have either not been recorded or have been observed in low abundance, such as tiny scale barb Thynnichthys thynnoides (lomah) and barb Puntioplites bulu (tengalan).Apparently, the current state of pollution, eutrophication, invasive predatory species, and unregulated illegal fishing and overfishing pose significant risks.Without proper management, these factors could lead to further reduction in native fish populations.
Water quality degradation has also affected the biodiversity of Laguna Lake.Migratory species from Manila Bay are no longer observed in the lake.This is attributed to the poor water quality of the Pasig River, which connects these two water bodies.Despite the improved water quality of the Pasig River due to the appropriate programs implemented by the Department of Environment and Natural Resources, migratory species like the flatfish "kitang" (Scatophagus sp.) is still not evident in the lake.
There is limited detailed biodiversity data available for Beung Kiat Ngong, consistent with other parts of Lao PDR.With the increase in the population, the balance of resources is lost, and the use of hunting equipment becomes diverse, including the electric shocker [38,39].Consequently, this problem has led to a decrease in biodiversity.The promotion on conservation awareness is not strong enough, thereby resulting in biodiversity loss as the main concern in the Beung Kiat Ngong

Climate change
Climate change is a prevalent threat to aquatic ecosystems.Among the manifestations of human-induced climate change are increased temperature and irregular rainfall regimes.These changes disrupt the hydrology, ecology and other functioning of water bodies, which subsequently may alter the livelihoods of the residents.These unpredictability and wide-ranging impacts of climate change pose a significant challenge to lake management, requiring adaptive and flexible management strategies.For example, in Songkhla Lake, a survey involving 271 farmers revealed that the primary issue was a decline in agricultural productivity caused by shifting weather patterns [40].This finding highlights the urgent need for comprehensive interventions to mitigate the effects of climate change on agriculture, particularly among farmers involved in fruit cultivation and fishing activities.Similarly, in Malaysia, it was reported that variables in rainfall pattern and intensity due to global warming affect the lakes' ability in controlling the flood and drought [41].

Challenges in managing lake ecosystems
There are barriers to lake management in ASEAN countries, related to local socio-economic, political landscape and governance.

Intersectoral Coordination and Governance/ Stakeholders
One of the prominent challenges we identified is related to institutional issues.There are numerous authorities (e.g., ministries and departments) that regulate and manage various water sectors.Sometimes this creates duplication of efforts.In Laguna Lake for example, the mandate to manage and develop the lake and the Laguna de Bay Region with due regard to environmental protection and ensuring the quality of human life and ecological systems was given to the Laguna Lake Development Authority (LLDA).Although LLDA is mandated by law to perform its function as a basin-wide authority, there are several government institutions that also exercise their respective mandate in the same region.This has led to overlapping areas of jurisdiction with other government agencies in terms of policy and planning, regulation and infrastructure development [42].Likewise, there is lack of coordination by some local government units with the LLDA regarding development projects.
In Temengor Reservoir, several stakeholders engaged in lake management and utilization were identified.These stakeholders represent diverse interests and utilization of this lake and its surrounding resources [43], leading to a fragmentation of management and administration.These stakeholders include Orang Asli (indigenous people), who have a long history of inhabiting the area.The Orang Asli community claims the Temengor Reservoir as their ancestral territory, having settled in the region prior 1313 (2024) 012017 IOP Publishing doi:10.1088/1755-1315/1313/1/01201710 to the creation of the lake.They are granted certain privileges, that allow them to reside around the lake.However, despite these benefits, the Orang Asli still struggle with development challenges due to limited education and training opportunities.The lack of effective coordination and integration of data and information among these stakeholders has prevented the adequate quantification of the lake's value [44].
The lack of political will for strict environmental regulations, coupled with low public awareness regarding the significance of lake ecosystem conservation, may impede progress.One primary reason for this limited awareness among Songkhla Lake residents stems from unmet basic needs, such as financial security, which diverts their focus from lake conservation efforts [45].Consequently, sustainable solutions should be integrative, involving collective decision-making, joint problem-solving, and participatory assessment.
The Beung Kiat Ngong wetlands is very important to the surrounding community.However, community participation is remains poor, and although the management plan is in place, the results have been less than favourable.The management Buang Kung Nong wetlands is unsatisfactory due to incoordination between government units.

Resource limitations
One of the major challenges in enforcing strict monitoring and management strategies is the limited availability of resources.These limitations encompass various aspects such as funding, technology, and personnel.Insufficient financial support hinders the implementation of effective measures to monitor and manage natural disasters.Additionally, a lack of advanced technological tools can impede efforts to accurately predict climate variability patterns.Moreover, inadequate staffing levels pose difficulties for conducting comprehensive monitoring and implementing timely interventions.By securing additional funding, there would be an opportunity to invest in state-of-the-art technologies like weather forecasting systems with improved accuracy and early warning capabilities.

Discussion
As societies and their need for ecosystem services continue to grow, the importance of inland water bodies increases.Despites playing important ecological roles, inland water bodies are threatened by various anthropogenic stressors, that led to degradation and increasing vulnerabilities.The rehabilitation of aquatic ecosystems is now integrated into management and engineering practices which requires allocation of management costs that impose constraints on government budgets.As lakes are regarded as socio-ecological systems, there is a need for the governance structures and management systems to prioritize in achieving balance between the environment, economy, and social needs [44].Determining the lake carrying capacity for various uses is crucial, instead of concentrating on a particular use such as aquaculture.
The management of such complex ecosystems requires dealing with inherent challenges.Our review identified that selected water bodies have typical issues, such as fragmented management and administration, lack of intersectoral coordination and governance, and insufficient enforcement measures.Integration and coordination are the key elements in resource management be it on the policy level, implementation, resource mobilization and stakeholder participation especially when several stakeholders are involved.In addition, watershed management is very important.All lake managers, policy and decision makers and key stakeholders should be aware of the conflicts in upstreamdownstream land use and the associated cascading impacts, due to the complex dynamics of lake ecosystems [44].Thus, it is important to include watershed planning and development in environmental management target, so that a sustainable lake water quality management could be implemented.
It is imperative for effective lake management to be guided by the Integrated Lake Basin Management (ILBM) Approach, which is supported by six pillars, namely institutions, policies, finance, technology, participation, and science.For example, the LLDA has adopted ILBM to manage Laguna Lake where this semi-government corporation has been actively promoting demand-driven research, emphasizing on data needs and studies to support policy decisions.Similarly, in Malaysia, several waterrelated thematic studies were conducted, led by the Academy of Sciences Malaysia (ASM) to expedite the nationwide implementation of Integrated Water Resource Management (IWRM), referred to as National Integrated Water Resources Management Plan (NIWRMP).In Songkhla Lake, this framework is being addressed through the implementation of strategic plans, like the 5-Year Strategic Plan for the Special Development Area of the Songkhla Lake Basin.
Moreover, resource limitations hinder effective lake management; there is a need for funding, technology, and staffing for comprehensive monitoring and timely interventions.This financial barrier has been effectively tackled by LLDA in their management of Laguna Lake.The LLDA does not depend solely on the National Government for funds, but it secures local and international funding support such as policy development, research, infrastructure, and community-based projects.As a semi-government corporation, LLDA generates its own revenues from investments, resource user fees, fines and penalties, laboratory services and permits.A portion of the environmental user fee is allocated for environmental projects not only by the authority but can also be availed by the Watershed Management Councils for water quality improvement.

Conclusion
There are drivers that affect aquatic ecosystem health, and barriers that hinder its effective management and resilience.A multi-dimensional approach is required, encompassing rigorous governance, strategic resource allocation, and fostering public awareness to sustain the ecosystem health of these ecosystems.Future studies may further explore the effective community participation and the potential of technological advancements for lake management.It is time for the Governments to include the lake and inland waters in general as a prominent resource in the national water agendas, aligned with the present Decade for Ecosystem Restoration.On the same note, the United Nations Environment Assembly has unanimously passed the Resolution on Sustainable Lake Management in 2022 which serves as a resounding call to action for all stakeholders of every lake in every nation.

Figure 1 .
Figure 1.Maps of selected water bodies from each core member country of SEALNet; (A) Batur Lake, Indonesia (Modified from Final Report of Local Government of Bangli Regency & Faculty Marine and Fisheries -Udayana University, 2017), (B) Temengor Reservoir, Malaysia, (C) Songkhla Lake, Thailand, (D) Laguna de Bay, Philippines and (E) Beung Kiat Ngong Wetland, Laos.