Modeling the spatio-temporal flow dynamics of groundwater-surface water interactions of the Lake Tana Basin, Upper Blue Nile, Ethiopia

Abstract

The Ethiopian government has selected Lake Tana basin as a development corridor due to its water resources potential. However, combined use of groundwater (GW) and surface water (SW) is still inadequate due to knowledge gaps about the flow dynamics of GW and SW. Mostly, there is no information about groundwater use. Therefore, this study aims to investigate the dynamics of GW-SW interactions on a spatio-temporal basis in three of the main catchments (Gilgelabay, Gumara and Ribb) that drain into Lake Tana. To this end, the SWAT-MODFLOW model, which is an integration of SWAT (Soil and Water assessment Tool) and MODFLOW, is used. The results reveal strong hydraulic connection between the GW and SW in all the three catchments. In the Gilgelabay catchment, the flow from the aquifer to the river reaches dominates (annual discharge from the aquifer varies from 170 to 525,000 m3/day), whereas in Gumara (annual exchange rate between −6,530 and 1,710 m3/day) and Ribb (annual exchange rate between −8,020 and 1,453 m3/day) the main flow is from the river reaches to the aquifer system. The flow pattern differs in the three catchments due to variations of the aquifer parameters and morphological heterogeneity. Overall, this study improves our understanding of GW-SW flow dynamics and provides insights for future research works and sustainable water management in the Nile region.

To What Extent Is Hydrologic Connectivity Taken into Account in Catchment Studies in the Lake Tana Basin, Ethiopia? A Review

“…Some studies used SWAT to evaluate the effect of rainfall on: (1) surface flow, e.g., [45,48,51,[53][54][55]60,61]; (2) surface flow and subsurface flow, e.g., [58,59,83]; (3) surface flow and sediment flow, e.g., [50,57,68]; (4) sediment flow, e.g., [65,94]; (5) lake level, e.g., [95]; (6) drainage ratio, e.g., [96]; (7) soil erosion, e.g., [97]; and (8) flood hazard, e.g., [46]. Other studies used SWAT to analyze the impact of soil and water conservation measured on (1) surface flow and subsurface flow, e.g., [64], and (2) surface flow and sediment flow, e.g., [68,76,78]. Only few studies used SWAT to quantify the impact of land use/land cover on (1) surface flow, e.g., [70], and (2) surface flow and subsurface flow, e.g., [66,71].…”

“…[96]; (7) soil erosion, e.g., [97]; and (8) flood hazard, e.g., [46]. Other studies used SWAT to analyze the impact of soil and water conservation measured on (1) surface flow and subsurface flow, e.g., [64], and (2) surface flow and sediment flow, e.g., [68,76,78]. Only few studies used SWAT to quantify the impact of land use/land cover on (1) surface flow, e.g., [70], and (2) surface flow and subsurface flow, e.g., [66,71].…”

Challenges and Prospects of Advancing Groundwater Research in Ethiopian Aquifers: A Review

“…Increasing human demand for groundwater and variability in recharge affects groundwater contribution to surface water and ultimately are a supply of concern for future groundwater management. The Soil and Water Assessment Tool (SWAT) coupled with MODFLOW (SWAT-MODFLOW) were also applied to determine the recharge process through surface watergroundwater interactions [10,21]. The studies disclosed that robust interactions between the stream and groundwater advance flow dynamics of hydrogeological conditions.…”

“…In Ethiopia, the integrated development of surface water-groundwater interactions is still scarce due to knowledge gaps of the subject [21]. The surface water-groundwater interactions impact water quantity and quality in aquifers and surface water bodies [22].…”

Influences of land use changes on the dynamics of water quantity and quality in the German lowland catchment of the Stör

“…The Soil and Water Assessment Tool (SWAT) is a process-based and semi-distributed eco-hydrological model with a continuous time step (Arnold et al, 1998). It is suitable for the simulation of streamflow, sediment, nutrients, and groundwater dynamics in catchments of different sizes (Aghsaei et al, 2020;Bieger et al, 2014;Haas et al, 2016;Tigabu et al, 2020). The computation of water routing, nutrient cycles and soil erosion is based on hydrologic response units (HRUs) characterized by the same land use, 150 soil type, and slope in the same subbasin representing the spatial heterogeneity of the catchment (Arnold et al, 2013).…”