Many calibration techniques have been developed for the Soil and Water Assessment Tool (SWAT). Among them, the SWAT calibration and uncertainty program (SWAT-CUP) with sequential uncertainty fitting 2 (SUFI-2) algorithm is widely used and several objective functions have been implemented in its calibration process. In this study, eight different objective functions were used in a calibration of stream flow of the Pursat River Basin of Cambodia, a tropical monsoon and forested watershed, to examine their influences on the calibration results, parameter optimizations, and water resources estimations. As results, many objective functions performed better than satisfactory in calibrating the SWAT model. However, different objective functions defined different fitted values and sensitivity rank of the calibrated parameters, except Nash–Sutcliffe efficiency (NSE) and ratio of standard deviation of observations to root mean square error (RSR) which are equivalent and produced quite identical simulation results including parameter sensitivity and fitted parameter values, leading to the same water balance components and water yields estimations. As they generated reasonable fitted parameter values, either NSE or RSR gave better estimation results of annual average water yield and other water balance components such as annual average evapotranspiration, groundwater flow, surface runoff, and lateral flow according to the characteristics of the river basin and the results and data of previous studies. Moreover, either of them was also better in calibrating base flow, falling limb, and overall the entire flow phases of the hydrograph in this area.

Artificial capillary barriers (CBs) are used to improve root zone conditions as they can keep water and nutrients in the root zone by limiting downward percolation. Numerical analysis is one of the promising tools for evaluating CB systems’ performance during the cultivation of leafy vegetables. This study aims to investigate the effects of the CB system on soil water dynamics during spinach cultivation in a soil column under different irrigation scenarios using HYDRUS (2D/3D) by comparing uniform (UNI), line-source (LSI), and plant-targeted (PTI) irrigations combined with alternative irrigation schedules. Simulation results of volumetric soil water contents were generally corresponding to measured data. Simulation results with various hypothetical irrigation scenarios exhibited that the CB was an effective system to diminish percolation losses and improve the root zone’s soil water storage capacity. On the other hand, evaporation loss can be increased as more water is maintained near the surface. While this loss can be significantly minimized by reducing the water application area, the irrigation amount must be carefully defined because applying water in a smaller area may accelerate downward water movement so that the water content at the CB interface can reach close to saturation. In addition to the malfunction of the CB layer, it may also cause a reduction of plant root water uptake (RWU) because the root zone is too wet. Among evaluated irrigation scenarios, irrigating every two days with PTI was the best scenario for the spinach as water use efficiency was greatly improved.

Boeng Sneh Lake (BSL), a 3,924-hectare freshwater wetland in Cambodia’s Mekong Delta, is a critical water resource that supports agriculture, domestic water supply, fisheries, biodiversity conservation, and flood regulation. This study assessed the lake’s hydrological dynamics and their implications for Integrated Water Resources Management (IWRM) under growing pressures from climate variability and increasing water demand. Using an integrated socio-hydrological approach, this study combined a decade of meteorological data (2014–2024), remote sensing analysis, a bathymetric survey comprising 121 systematic depth measurements supplemented by 19 targeted measurements within the nine deep pools, stakeholder consultations, and field investigations conducted in 2025. The findings revealed pronounced seasonal fluctuations in lake storage, with wet-season volumes reaching 80–100 million m³ but declining to critical levels of 5–15 million m³ during recent dry seasons, well below the operational threshold of 27 million m³ required to sustain the domestic water supply and ecological refugia. Expanding irrigation for triple-cropped rice and increasing domestic water abstraction have intensified competition among water users, threatening fisheries and ecosystem health in the region. This study highlights the value of a Google Earth Engine-based monitoring platform and the District Technical Working Group (DTWG) as innovative tools for evidence-based collaborative water governance. It recommends a trigger-based water allocation framework, demand management measures, enhanced hydrological monitoring, and stronger institutional coordination to improve the resilience and sustainability of BSL under future climatic and socioeconomic pressures.

Boeng Sneh Lake is a crucial freshwater ecosystem supporting rice farming, fisheries, water supply, and climate resilience for nearby communities. Its sustainability is threatened by rising water demand, climate- and human-driven hydrological changes, and competing sector needs. The District Technical Working Group (DTWG), a multi-sectoral, ecosystem-based governance model for water management, was piloted to coordinate water users around the lake; however, effective water management is hindered, among other factors, by limited locally accessible data. Existing water datasets are often available at central levels but are fragmented, poorly disaggregated, and rarely integrated into operational tools used by local authorities. The priority is therefore not simply more data collection, but rather improving local access, integration, and decision-making empowerment. Dedicated budget allocations for water-related data collection, monitoring and management should be incorporated into decentralised planning, including commune development and investment plans. Without reliable data, lake water management remains reactive, fragmented, and vulnerable to conflicting sectoral demands. This shows that operational hydrological information enables local institutions to manage shared water resources effectively, providing strong evidence for the government to expand the pilot DTWG's data-driven community water management across Cambodia.