Abstract
Human population growth and land-use changes raise demand and competition for water resources. The Upper OumErRabia River Basin is experiencing high rangeland and matorral conversion to irrigated agricultural land expansion. Given Morocco’s per capita water availability, River-basin hydrologic modelling could potentially bring together agricultural, water resources and conservation objectives. However, not everywhere have hydrological models considered events and continuous assessment of climatic data. In this study, HEC-HMS modelling approach is used to explore the event-based and continuous-process simulation of land-use and land cover change (LULCC) impact on water balance. The use of HEC-GeoHMS facilitated the digital data processing for coupling with the model. The basin’s physical characteristics and the hydro-climatic data helped to generate a geospatial database for HEC-HMS model. We analyzed baseline and future scenario changes for the 1980-2016 period using the SCS Curve-Number and the Soil Moisture Accounting (SMA) loss methods. SMA was coupled with the Hargreaves evapotranspiration method. Model calibration focused on reproducing observed basin runoff hydrograph. To evaluate the model performance for both calibration and validation, the Coefficient of determination (R2), Nash-Sutcliffe efficiency (NSE), Root Mean Square Error (RSR) and Percent Bias (PBIAS) criteria were exploited. The average calibration NSE values were 0.740 and 0.585 for event-based (daily) and continuous-process (annual) respectively. The R2, RSR and PBIAS values were 0.624, 0.634 and +16.7 respectively. This is rated as good performance besides the validation simulations were satisfactory for subsequent hydrologic analyses. We conclude that the basin’s hydrologic response to positive and negative LULCC scenarios is significant both positive and negative scenarios. The study findings provide useful information for key stakeholders/decision-makers in water resources.
Highlights
Morocco like the most countries, experiences anthropogenic pressure and land-use dynamics in and around mountainous basins [1] [2]
In the Upper OumErRabia River Basin (UOERRB), land-use and land cover change (LULCC) trends mainly involve the conversion of rangeland and matorral to irrigated agriculture and forestry
Land-Use and Land Cover Change Impact Analysis We focused on determining the major LULCC based on the 2002 and 2016 LULC maps
Summary
Morocco like the most countries, experiences anthropogenic pressure and land-use dynamics in and around mountainous basins [1] [2]. The interactions among land-uses, soil types, vegetation cover, climate variability and subsequent impact on hydrologic behaviors of watersheds have been studied by various researchers [3]-[9]. More people have settled around the OumErRabia (OER) due to favorable climate increasing the overall basin’s population. This has raised demand and competition for land, water and food resources [10] and leading to irrigated agriculture expansion. Most recent land-use studies conducted in the OumErRabia (OER) basin are limited to water quality variation [17] and soil fertility impact [18]
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