Analysis of water balance and hydrodynamics of Lake Beseka, Ethiopia

Abstract

This study aims to calculate the water balance, interaction with irrigation water inflow, and hydrodynamics of the Lake Beseka by a spreadsheet-based model using climatic, hydrological, multi-temporal satellite images, groundwater, and lake chemistry data. The rainfall for the catchment was estimated as 558.4 mm/year, whereas the mean evaporation was computed as 2,214 mm/year by the Penman method. The annual direct rainfall contribution to the lake was obtained to be 25.84 MCM (million cubic meters) and a runoff inflow in the catchment area of 37.2 MCM. This balance pointed to the mean evaporation of 108.2 MCM/year in the lake indicating that the water inflow was greater than the outflow. A major cause for the rise of the lake level was the drainage of excess irrigation water toward the lake, mainly from the Fentale Irrigation Farm. The average increment of the groundwater level in the area was 12 cm/year from 2010 to 2014. From 1998 to 2014, the electrical conductivity was reduced by 25.6%, and calcium was increased by 96%. The study outlined that appropriate irrigation drainage should be implemented in the catchment to ensure the balance between the rainfall, infiltration, and surface runoff to optimize economic and social welfare in the area.

Evaluation of water balance in the Jaro Irrigation area, Tabalong Regency, South Kalimantan Province

“…Before being used for data analysis, it is necessary to validate and correct TRMM rainfall data for 2000 -2019 with observation posts using the Correlation Coefficient method which produces a determination value and continues data correction by selecting the regression equation with the highest determination value. The regression equation used is linear, geometric, logarithmic, and exponential regression (Gichamo et al, 2022;Ezuar et al, 2018). The criteria for the determination value (R2) according to Setyorini & Hardaningrum (2020), is a very low interpretation is 0.00-0.199, Low is 0.20-0.399, moderate is 0.40-0.599, strong is 0.60-0.799 and very strong is 0.80-1.000.…”

The Shrinking and Expanding Eastern Africa Rift Valley Lakes: The Case of Ethiopian and Kenyan Rift Valley Lakes: Review

“…Unlike other rift valley lake watersheds, the catchment of the Lake Beseka does not contain perennial river that drains into the lake, except seasonal floods in the wet season, in addition to excess irrigation drainage and groundwater inflow [89]. The lake was essentially a surface pond of about 2.7 km 2 total surface area in the late 1950's and early 1960's before the establishment of Metahara Sugar Estate [7,97].…”

“…Although the starting time of expansion is not exactly known, most previous studies tend to agree that the problem was initiated in the late 1960 and early 1970s when the Metahara mechanized farm around the lake was started to be irrigated for cultivation of cotton and citric fruits which latter on shifted to sugarcane development [7,12,85,97,98]. Furthermore, [89] reported that the water level of Lake Beseka started to rise from 1976 to 1978 as a result of poor irrigation water management practices of the newly introduced Abadir farm.…”

“…The Extent and Pattern of Expansion of Lake Beseka Lake Beseka has been gauged since 1976, but some data between 1999 and 2001 were missing related to the damage at the station [89]. Since Lake Beseka's morphometric data were initially reported by Wood & Talling, (1988), many scholars have cited this value of 3.2 km 2 in different research articles, until very recently.…”