Abstract
Socioeconomic development in watersheds lead to land-use changes, which can alter water and sediment inflows into reservoirs, leading to uncertainty in water supply reliability. A modelling framework coupling the Soil and Water Assessments Tool (SWAT) and the @RISK genetic algorithm optimisation tool was developed to optimise water allocation and estimate water supply reliability under uncertainty in future land-use. The multi-purpose Nuicoc reservoir in Vietnam was used as a case study. Modelling results showed that an expansion of the urban areas by 10% and conversion of 5% of the forest to agricultural areas produced the highest water releases for downstream demands of all simulated scenarios, with 5 Mcm/year greater water releases than the baseline for the case where sedimentation was not considered. However, when sedimentation was considered, it generated the greatest decrease in water releases, with 6.25 Mcm/year less than the baseline. Additionally, it was determined that spatial distribution of land-use significantly affect sediment inflows into the reservoir, highlighting the importance of targeted sediment management. This demonstrates the usefulness of the proposed framework for decision-makers in assessing the impact of possible land-use changes on the reservoir operation.
Highlights
Available freshwater resources in rapidly developing countries are becoming scarce due to higher demands from industrial, recreational, municipal, and agricultural sectors [1,2]
The results showed that about 13 million cubic meters (Mcm) of sediment had been transported into the reservoir [47]
The P-factors indicate that 79% and 75% of observed data was within the 95PPU range in the calibration and validation, respectively (Figure 6, Table 2)
Summary
Available freshwater resources in rapidly developing countries are becoming scarce due to higher demands from industrial, recreational, municipal, and agricultural sectors [1,2]. Socioeconomic developments can lead to significant changes in land-use, which can subsequently impact on water resources critical for downstream economic development [3]. Urbanisation and conversion from forest to agriculture induce changes in evapotranspiration, surface runoff, groundwater and streamflow, which affect water supply to reservoirs, and cause soil erosion and the transport of sediment to reservoirs, which can have an effect on the water storage capacity and operation of a reservoir [3,6]. Changes in forest, urban and agricultural land-use areas in a reservoir watersheds can cause changes in the way water in a reservoir is managed [3,7]. Assessing the impacts of future land-use change on a reservoir’s water supply reliability is essential
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