Hydrological Modeling of Artificial Recharge of Groundwater for Sustainable Water Supply in Dodoma City

Abstract

Groundwater is an important resource that supports the life of people and the surrounding ecosystem in the world. It is the primary source of safe water to semi-arid areas characterized by limited surface water. In Africa, water scarcity has been hitting major cities and towns. In Tanzania, Dodoma has long experienced shortages of water. Owing to the recent transfer of all significant offices from Dar es Salaam to Dodoma, the City's population has drastically increased. The primary source of water in the City is the Makutupora aquifer. The growing human population has resulted in high demand for water use, which has led to the overexploitation of groundwater aquifer. Therefore, this study was carried out using a Modular finite-difference flow model (MODFLOW) to model artificial recharge products to replenish groundwater in the Makutupora aquifer to ensure water supply sustainability in the City. Before simulation of the artificial recharge was done, groundwater storage was estimated using available borehole data and GIS technique. The results indicated that the total groundwater storage in the Makutupora aquifer was about 24.8 BCM (Billion Cubic Meters). The MODFLOW packages used include well package (WEL), General Head Boundary Package (GHB), Evapotranspiration package (EVT), Drain package (DRN), and Recharge Package (RCH). A total of 21 piezometers were used for model calibration. The statistical calibration was also done to validate the model's calibrated parameters. After simulation of the steady-state reference period, the other four stress periods were simulated, considering the projected population and water demand. The planned injection wells to the model in the first, second, third, and fourth transient state periods resulted in a safe yield of 168,857 m 3 /day, 197,760 m 3 /day, 360,000 m 3 /day, and 600,430 m 3 /day, respectively. The recommended artificial recharge source is water from the Kinyasungwe River that flows during rainfall time, generally from November to May. One of the W. P. Venance, G. V. Lugomela and V. G. Masanja 2 recorded years (2007) indicated a flow of up to 23.646 Million Cubic Meters (MCM). The recommended artificial recharge is possible due to the aquifer's storage capacity of 247.84 Million Cubic Meters (MCM).Other flows in small streams within the well field were recommended in creating artificial recharge structures to add more water to the aquifer and natural recharge. Therefore, information from this study could be used by engineers when constructing artificial engineering structures to replenish the water pumped from the Makutupora aquifer.