Spatial and seasonal groundwater quality assessment for drinking suitability using index and machine learning approach.

Spatial and seasonal evaluation and monitoring of groundwater (GW) quality is essential for the sustainable management of this priceless resource and the provision of safe drinking water. Nevertheless, GW quality appraisal was not given due attention in the current study area (flat terrain part of the Tana sub-basin). This study sought to assess the seasonal and regional physicochemical GW quality parameters for drinking appropriateness using the drinking water quality index (DWQI) and support vector machine (SVM). The main cations in both the dry and wet study seasons were, in decreasing order, Na+, Ca2+, Mg2+, K+, and Fe2+, according to the results. Conversely, the main anions were HCO3-, CO32-, Cl- or NO3-, SO42- and PO43-, ordered from higher to lower. During the two research seasons, Ca-HCO3 and Na-HCO3 were the predominant water types based on Piper diagram results. Reverse ion exchange and evaporation were the principal hydrogeochemical processes that control the hydrogeochemistry identified by Durov and Gibbs diagrams, respectively. Excellent GW quality class for drinking was demonstrated by the majority of geographical and seasonal DWQI readings over the two seasons. Nevertheless, during the rainy season, there was a noticeable decline in the GW quality condition around the northern shores of Lake Tana. Therefore, it is advised to implement comprehensive GW quality protection measures and improve system management to mitigate pollution to reduce health hazards in the examined region.

Long-term spatiotemporal dynamics of groundwater storage in the data-scarce region: Tana sub-basin, Ethiopia.

Imprudent extraction of groundwater tends to undue stress and portends its sustainability. Spatiotemporal analysis of groundwater storage anomaly (GWSA) is imperative for the judicious use, management, and sustainable development of a region. This study aimed to examine the changes in groundwater storage over the past 20 years in the Tana sub-basin using Gravity Recovery and Climate Experiment (GRACE) assimilated into Global Land Data Assimilation Systems (GLDAS). Validation analysis was carried out to evaluate the accuracy of GWSA against anomalies of Lake Tana water level, precipitation, and in-situ groundwater level. Modified Mann-Kendal test and Sen's slope estimator were applied for trend analysis of the GWSA. The results exhibited that GWSA strongly correlated (Pearson's correlation coefficient, R ranges from 0.75 to 0.96) with the three validation above variables, which elucidated in general, credible GWSA estimation. The net annual GWSA curve showed a non-significant (p > 0.05) decreasing trend from 2003 to 2012. However, years including 2005, 2006, and 2009 were drought periods, which caused 0.49 billion cubic meters (BCM) groundwater loss. In the entire study period (2003-2022), on the other hand, the net annual GWSA revealed a significant increasing trend (p < 0.05) with a rate of 0.333 cm/year. Generally, the Tana sub-basin was nurtured with a net 4.87 BCM groundwater gain in the study period. The most sensitive parts of the study area to large fluctuations of groundwater storage were mainly the nearby southern and eastern directions of Lake Tana.

The Secret of the Main Campus Water-Wells, Arba Minch University, Ethiopia.

Groundwater is one of the precious water sources for domestic, irrigation, and industrial demands in arid and semiarid regions of the world. The same is true in Ethiopia context. In this study, seven groundwater samples were collected and analyzed for various chemical constituents (pH, TDS, Na+, K+, Ca2+, Mg2+, SO4 2-, Cl-, HCO3 -, and NO3 -) to assess the hydrogeochemical characteristics and water types of the groundwater wells. Among the seven sampled groundwater wells, five wells are found and used for domestic water supply in Arba Minch University (AMU) main campus. The remaining two are used for industrial and irrigation demands located at the compound of Textile Factory and Haile Resort, respectively. Results showed that the main campus groundwater wells are saline and harder than the two wells from Textile Factory and Haile Resort. Moreover, elevated concentration of nitrate and potassium (greater than the maximum permissible level allowed in Ethiopia) were obtained in the groundwater sources used mainly in the AMU main campus wells. These elevated concentrations of potassium and nitrate beyond the enriched salt contents in the AMU main campus wells could pose kidney, cardiovascular, and other related health problems. This study, therefore, recommends the AMU to find other groundwater sources for drinking purpose other than the studied water-well field.