Abstract
Predicting the impact of climate change and human activities on river systems is imperative for effective management of aquatic ecosystems. Unique information can be derived that is critical to the survival of aquatic species under dynamic environmental conditions. Therefore, the response of a tropical river system under climate and land-use changes from the aspects of water temperature and dissolved oxygen concentration were evaluated. Nine designed projected climate change scenarios and three future land-use scenarios were integrated into the Hydrological Simulation Program FORTRAN (HSPF) model to determine the impact of climate change and land-use on water temperature and dissolved oxygen (DO) concentration using basin-wide simulation of river system in Malaysia. The model performance coefficients showed a good correlation between simulated and observed streamflow, water temperature, and DO concentration in a monthly time step simulation. The Nash–Sutcliffe Efficiency for streamflow was 0.88 for the calibration period and 0.82 for validation period. For water temperature and DO concentration, data from three stations were calibrated and the Nash–Sutcliffe Efficiency for both water temperature and DO ranged from 0.53 to 0.70. The output of the calibrated model under climate change scenarios show that increased rainfall and air temperature do not affects DO concentration and water temperature as much as the condition of a decrease in rainfall and increase in air temperature. The regression model on changes in streamflow, DO concentration, and water temperature under the climate change scenarios illustrates that scenarios that produce high to moderate streamflow, produce small predicted change in water temperatures and DO concentrations compared with the scenarios that produced a low streamflow. It was observed that climate change slightly affects the relationship between water temperatures and DO concentrations in the tropical rivers that we include in this study. This study demonstrates the potential impact of climate and future land-use changes on tropical rivers and how they might affect the future ecological systems. Most rivers in suburban areas will be ecologically unsuitable to some aquatic species. In comparison, rivers surrounded by agricultural and forestlands are less affected by the projected climate and land-uses changes. The results from this study provide a basis in which resource management and mitigation actions can be developed.
Highlights
The water temperature in a river system determines the availability, activities, and type of aquatic life in the ecosystem in which it belongs [1]
The gauge station for streamflow and water quality were in different locations (Figure 1b); the hydrological modeling result was separated from the water temperature and dissolved oxygen (DO) concentration models
Five parameters were more sensitive out of the thirteen parameters adjusted during the calibration processes: Lower zone nominal soil moisture storage (LZSN), Index to infiltration capacity (INFILT), Lower zone evapotranspiration (ET) parameter (LZETP), Base groundwater recession (AGWRC), and Upper zone nominal soil moisture storage (UZSN) parameter
Summary
The water temperature in a river system determines the availability, activities, and type of aquatic life in the ecosystem in which it belongs [1]. Its physical properties depend on climatic variables [2], such as air temperature [3,4], and precipitation [5]. The evaluation of the impact of climate change on river water temperature and its influences on dissolved oxygen (DO). Climate 2017, 5, 58 availability in some climate groups illustrates that a variation of DO concentrations, either higher or lower, can result in water quality deterioration and distortion of an aquatic ecosystem [10,11,12,13,14]. Other local conditions, such as land-use, pollution levels, and local hydrology increase or decrease its variability [16,17,18]
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