Long-term interaction between land use patterns and water quality in tropical reservoirs

Land use and land cover changes (LULCs) have affected the integrity and quality of water resources globally, especially in Vietnam, where the economy highly depends on agricultural land. LULC has degraded many waterbodies in the region, such as Tri An Reservoir (TAR), one of the largest freshwater bodies in Southern Vietnam. This study investigated the long-term interaction between land use patterns and water quality in the TAR Basin (TARB). Land-use types and landscape metrics were used to investigate the correlation with water physico-chemical variables at watershed scale. The results indicated that dense forest area was the most important factor influencing turbidity, dissolved inorganic nitrogen (DIN), and total phosphorous (TP), while the proportion of perennial/orchard mostly influenced total suspended solids (TSS). The built-up/residential area significantly influ-enced turbidity, TSS, and total dissolved solids (TDS). Several landscape metrics correlated properly with turbidity, indicating that land-use types and landscape metrics in TARB significantly influenced water quality in TAR. Over the past two decades, TAR has experienced degradation in water quality mainly due to eutrophication with increas-ing trends of nitrogen and phosphorus. To improve water quality and control water eutrophication, future research should consider reducing nitrogen and phosphorus inputs.