Analysis of River Tributaries’ Streamflow Contribution Using WEAP Model: A Case of the Ngwerere and Kanakatampa Tributaries to the Chongwe River in Zambia

Abstract

Ngwerere and Kanakatampa Streams are the main tributaries of the Chongwe River. The Ngwerere stream originates from the city of Lusaka and meanders through Lusaka City and Chongwe Town for an approximate distance of 41 km before joining into the upper part of Chongwe River. The Kanakatampa Stream is a tributary of the Chongwe River. It meanders from the Kanakatampa Area for approximately 52 km before discharging into the middle of the upper part of the Chongwe River. The Chongwe River Catchment which is a sub-catchment of the Zambezi Basin drew the attention of researchers and policymakers when the Chongwe River started drying up in the dry seasons causing a water crisis particularly in the downstream regions of the middle catchment. Therefore, it is important from the water resources management perspective, to assess the contribution of tributaries into the flows of the Chongwe River. Ngwerere and Kanakatampa streams are socially, economically, and environmentally important streams for the city of Lusaka and surrounding area. This study, therefore, concentrated on evaluating the flow contribution of the two streams to the Chongwe River using the Water Evaluation And Planning (WEAP) tool. The streamflow data recorded at the Chongwe Great East Road Bridge gauging station were used in the WEAP embedded Parameter ESTimation (PEST) auto-calibration tool to calibrate (1970-1999) and validate (2000-2010) the model. The monthly streamflow model calibration and validation results were assessed using the How to cite this paper:

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“…For "d", the results were 0.882 and 0.909 during the model calibration and validation, respectively. [58,83,84] also achieved similar results to thos obtained in this work for the indexes mentioned above. NSE is influenced by high flows, leading to low coefficients [85], which can be considered for this work; some periods presented overestimated flows based mainly on the validation (Figure 3).…”

“…The parameters regarding the soil (Crop Coefficient, Retainment Capacity, Water Conductivity in the Radicular and Deep Zones, Resistance Runoff Factor, Preferential Flow Direction, and Storage Fraction at the Beginning of the Simulation of the Radicular and Deep Zones) were initially calibrated through an autocalibration tool integrated with WEAP, the Parameter Estimation Tool (PEST) [57], jointly with a manual adjustment approach [58][59][60].…”

Assessment of the spatiotemporal dynamics of the hydrological state of non-perennial river systems and identification of flow-contributing areas

“…Usually, the identification of flow-contributing areas is done using observed data from the tributary outlet (Tena et al, 2021); however, rainfall and physical characteristics (soil type, slope and land use and cover) can be used in the absence of the flow data. Several methods can be used to determine the contributing area, mainly proxies such as the Soil Conservation Service (SCS) Curve Number method and the runoff coefficients.…”

“…Modifying these contributing areas can induce alterations in the hydrological regime and subsequently impact the overall hydrological state. Identification of these areas often involves in-situ observations (Tena et al, 2021) and hydrological modelling (Golmohammadi et al, 2017). Additionally, there is potential to identify these areas utilizing easily accessible remote sensing data sources.…”