Recharge–Discharge Relations of Groundwater in Volcanic Terrain of Semi-Humid Tropical Highlands of Ethiopia: The Case of Infranz Springs, in the Upper Blue Nile

Abstract

The major springs in the Infranz catchment are a significant source of water for Bahir Dar City and nearby villages, while sustaining the Infranz River and the downstream wetlands. The aim of the research was to understand the hydrogeological conditions of these high-discharge springs and the recharge–discharge relations in the Infranz catchment. The Infranz catchment is covered by highly pervious and young quaternary volcanic rocks, consisting of blocky, fractured, and strongly vesicular scoriaceous basalt. At the surface, these rocks crop out as lineaments forming ridges, delimiting closed depressions in which water accumulates during the rainy season without causing surface runoff. Geology and geomorphology thus combine to produce very favorable conditions for groundwater recharge. Three groundwater recharge methods were applied to estimate groundwater recharge and the results were compared. Groundwater recharge was calculated to be 30% to 51% of rainfall. Rapid replenishment raises the groundwater level during the rainfall period, followed by a rapid decline during the dry season. Shallow local flow paths discharge at seasonal springs and streams, while more regional and deeper flow systems downstream sustain the high-discharge springs and perennial Infranz River. The uptake of 75% of spring water for the water supply of Bahir Dar City, local extraction for domestic and small-scale irrigation use from springs, rivers and hand-dug wells, encroaching farming, and overgrazing are exacerbating wetland degradation.

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

“…Tigabu, et al [83] studied the impact of rainfall variability on the groundwater head, and found that the peak of the groundwater head occurs one to three months after the peak of the rainfall. Nigate, et al [84] described how the average annual groundwater recharge calculated using the SMB approach for the five years (2012-2016) is 748 mm, or 51% of the rainfall.…”

“…Statistical analysis was employed in the Lake Tana basin to assess the impact of land and water management on hydrological processes [35,64,79,80]. In some publications, statistical models were used to assess: (1) the trend of rainfall and runoff, e.g., [126,127]; (2) groundwater recharge, e.g., [84]; (3) soil erosion, e.g., [128]; (4) lake level, e.g., [56,[129][130][131]; (5) phosphorus/dynamic, e.g., [132,133]; (6) sediment, e.g., [134][135][136]; (7) streamflow, e.g., [100,137]; and (8) water balance [138]. Statistical models were used to the address the hydrological response at the basin, subbasin and plot scale.…”

Downstream Consequences of Ribb River Damming, Lake Tana Basin, Ethiopia

“…The basin has three major aquifers: the Tertiary volcanic, the Quaternary volcanic, and the alluvio lacustrine sediments (Kebede, 2012;Nigate et al, 2016). The Trap Series (Oligocene to Miocene) volcanic flows and edifices, Quaternary basalt and Quaternary sediments (comprises alluvial lake deposits) are the main geological units of the basin and mainly found in the highlands and cliffs, in the lowlands and the floodplain along the lake coastline (Prave et al, 2016;Nigate et al, 2020). The surface area of the basin is dominated by Tarmaber Basalt with intercalated tuffs and basaltic lava flows (SMEC, 2008a).…”

Data quality deterioration in the Lake Tana Sub-basin, Ethiopia: scoping study to provide streamflow and water withdrawal data

“…Angereb reservoir is the main source of potable water for Gonder town (Getachew and Melesse 2012). Nigate et al (2020) reported that, since 2002, Areke and Lomi springs have been supplying municipal water for Bahir Dar town and the Infranz springs are being constructed to provide additional water supplies.…”