Assessing Water Availability and Unmet Water Demand Using the WEAP Model in the Semi-Arid Bweengwa, Kasaka and Magoye Sub-Catchments of Southern Zambia

Located in the semi-arid zone of Zambia, the Mutama-Bweengwa, Kasaka and Magoye sub-catchments have witnessed a high demand for water due to increase in population and socio-economic activities putting more pressure on water resources. This study assesses the hydrological components and ascertains the available water resources and unmet demand in the sub-catchments using the Water Evaluation And Planning (WEAP) Model and hydrometeorological data collected between 1951 and 2018. The model was calibrated and validated on 1971-1981 and 2008-2018 data respectively. The results reveal that the sub-catchments have transitioned from positive to negative water balance with -164.295 Mm3/year for Mutama-Bweengwa, -19.021 Mm3/year for Kasaka and -86.368 Mm3/year for Magoye. Evaporation was 1815.259 Mm3/year for Mutama-Bweengwa, 1162.655 Mm3/year for Kasaka and 1505.664 Mm3/year for Magoye. The demand for water has been increasing over time for various purposes such as irrigation, domestic, urban/rural water supply and livestock. The overall water storage in the sub-catchments showed a negative water balance for the year 2018. The observed and simulated peak streamflow were 8.16 m3/s and 7.7 m3/s occurring during the month of January and February respectively. The WEAP model performance achieved R2 of 0.98 during calibration and 0.95 for validation, and an NSE of 0.83 for calibration and 0.85 during validation. The values of objective functions show that the hydrology of the Mutama-Bweengwa, Kasaka and Magoye sub-catchments as predicted by the WEAP model provides satisfactory confidence for prediction of future streamflow and hence projection based on future scenarios.

Changes in hydrological regime in High Arctic non-glaciated catchment in 1979-2020 using a multimodel approach

Assessing hydrological consequences of climate change at the catchment scale is recently among key problems in hydrology.This study focuses on the estimation of changes in the hydrological regime in the Fuglebekken catchment in SW Spitsbergen(Svalbard).For this purpose,50 rainfll-runoff models were calibrated using available hydrometeorological observations.The models were validated based on archival flow and SWE observations,and proxy data from time-lapse cameras.Six models(FLEX-IS,GSM-SOCONT,PRMS,HBV,Nordic HBV,and GR4J)with the best performance were applied to reconstruct the past hydrological conditions and analyse the trends in flow regime in the period 1979-2020.Statistically significant changes at 0.05 level in the flow regime indicators were detected,including the number of days with the active flow during the calendar year(10.8 d per decade),during the mid-May-November period(9.8 d per decade),the date of the first day with the flow(-4.7 d per decade),and the last day with the flow during mid-May-November(8.4 d per decade).A statistically significant increase in runoff was estimated for two periods from mid-May to the end of June and the second part of August till mid-November.The changes in the first period result from increases in air temperature and earlier snowmelt-driven floods.An estimated runoff increase in the second period corresponds to large increases in rainfall.The increase in air temperature,earlier disappearance of snow,and decrease in precipitation in July and the first part of August result in runoff reduction.The presented results show that the Fuglebekken‘catchment's hydrological regime has already changed.The magnitude of the changes is larger compared to catchments located in lower latitudes.