Reservoirs are vital sources of water for agriculture, industry, and domestic uses. However, in the Ethiopian highlands, reservoir sedimentation is a growing challenge for dam operators as huge amounts of sediments accumulate behind dams, reducing storage capacity annually. Soil erosion worsens the problem by depleting fertile topsoil upstream and depositing sediment in downstream reservoirs, affecting rainfed and irrigated agriculture. This paper reviews sedimentation studies in reservoirs in the Ethiopian highlands and offers valuable insights into sedimentation thresholds for current and future reservoirs. Findings showed substantial sedimentation rates ranged from 4.7 to 16.2% a⁻¹ for decommissioned small reservoirs and from 1.7% to 3.6% a⁻¹ for functioning reservoirs. Moreover, annual sedimentation rates of 2.66% and 1.06% were, respectively, found for Angereb and Koga large-scale reservoirs. This indicated that sediment volume impoundment ranged between 66,489 and 30,309 m³/year for small reservoirs and 140,714 and 858,333 m³/year. This showed that the specific sediment volume was in the range of 2820–9171 m³/km²/year for small reservoirs while the value was between 2082 and 3902 m³/km²/year for large-scale reservoirs. It showed that the contribution of large catchment to reservoir area ratio and catchment shape indices was significant among other factors. The economic implications of losing reservoirs in the region was significant in that constructing new reservoirs with the same capacity as the abandoned ones ($ 1.3 million construction cost), would require approximately $18.5 million. Additionally, other direct and indirect costs, such as pollution, impacts on livelihoods, catchment area degradation, loss of reservoir area, and the decline of aquatic ecosystems, would have significant consequences in abandoning the reservoirs.

Assessing the available water resources and identifying suitable land for irrigation at the basin level is crucial for effective planning and decision-making in irrigation development projects. Therefore, this study aims to utilize Geographic Information System (GIS) and the Analytic Hierarchy Process (AHP) technique to evaluate surface irrigation suitability and surface water availability in the Beles Basin. Surface water availability was analyzed by constructing a flow duration curve (FDC) and assessing the 90% available flow of the Beles River. Meanwhile, land surface suitability was determined through GIS-based multi-criteria evaluation (MCE). This method integrates various factors including slope, proximity to rivers, soil characteristics (type, texture, depth, drainage), proximity to roads, and land use/land cover. These factors were weighted using pair-wise comparison matrices to determine their relative importance in assessing physical land suitability. The results revealed that approximately 13.84%, 73.05%, and 13.11% of the catchment area were highly, moderately, and marginally suitable for irrigation, respectively. Regarding water availability, the FDC analysis indicated that the Beles River maintains a 90% available flow of 1.6 m³/s throughout the year. Consequently, in December, the river can only irrigate 0.25% of the total irrigable land, whereas from May to September, it can irrigate the entire irrigable area. The river's low flow presents opportunities for extensive irrigation during the wet season but limits irrigation during the dry season. Therefore, the implementation of water storage structures is imperative to facilitate irrigation across the entire potential land during periods of low flow.

Assessing the quality of groundwater for better management of the water sources is essential. This study is aimed at evaluating the groundwater quality of Debre Tabor town. Twelve groundwater samples were collected at hand dung wells during the wet season (Mid July-Mid August 2020) and dry season (1st February –Mid-March 2021). Various Physico-chemical parameters (pH, electrical conductivity (EC), Total dissolved solids (TDS), Temperature, Turbidity, Calcium (Ca²⁺), Magnesium (Mg²⁺), Chloride (Cl⁻), Nitrate (No₃⁻), and microbiological parameters (Total coliform and Feacal coliform)) were analyzed and compared with the standard guidelines recommended by WHO. GIS was used to show the distribution of groundwater quality throughout the study area. WQI created by Canadian Council of Minster of the Environment (CCME) was applied to evaluate the suitability of the groundwater for drinking purposes. Also, the result shows that total coliform and faecal coliform at all groundwater wells were not suitable for drinking purpose. The result shows that Electrical conductivity, Temperature, Nitrate, Chloride and Magnesium at all groundwater wells were suitable for drinking purpose for both dry and wet season whereas Turbidity, pH, Calcium and Total Dissolved Solids are suitable for drinking purpose at some groundwater wells but not suitable at some wells. The water quality analysis result shows that spatial and seasonal variations of the parameters are significant throughout the study area(p < 0.05). According to CCMEWQI result seven groundwater samples show poor water quality status of 40.53-44 while, five groundwater samples show marginal water quality status of 44.19–55.82. Based on the information provided by the study, it is recommended to identify the source of contamination, provide properly designed sanitation systems and to monitor water quality at least once per year for effective and proper management of the groundwater quality.

The study was conducted to evaluate the performance of Selamko small scale irrigation scheme using internal and external performance indicators. The irrigation scheme command area was 63 ha and during the study season the irrigated area was 42ha. Over all activities in primary data collected included: field observation, discharge measurements in the canals, soil moisture before irrigation and after irrigation and depth of water applied at the field and interviewing beneficiary farmers. Secondary data were collected from secondary sources that were South Gondar Small Scale Irrigation coordination office, SGBoWR and WUA of the scheme. In order to evaluate the irrigation water, use efficiency of the scheme, nine farmer fields were selected from the scheme in relation to their location: at the head, middle and tail end water users. The internal process indicators which include conveyance efficiency and application efficiency were used to evaluate the performances of the scheme. From the analyses of internal performance indicators, the conveyance efficiencies were found to be 56.9% at the main canal, 57.09 at secondary canal 1 and 54.55% at secondary canal 2. The canals supply less water than the demand of the delivery points. And the application efficiencies were estimated to be 56.994%. The overall efficiency was 35.268%. The output per command area has to be calculated as 60198.14Birr/ha and 89738.1Birr/ha at 2016/17 and 2015/16 irrigation season respectively. The output per cropped area were estimated as 90297.62 Birr/ha and 99621.1 Birr/ha at 2016/17 and 2015/16 irrigation season respectively. The output per water consumed has to be determined as 17.66 Birr/m3 and 20.14 Birr/m3 at 2016/17 and 2015/16 irrigation season respectively. The water supply and irrigation supply were found as 1.71 and 1.47 respectively. From the analysis of physical performance of the scheme, during the study period, the irrigation ratio of the scheme was 66.67% and the sustainability of the scheme is 62.69% but in 2015/16 irrigation season, the irrigation ratio was 84.7% and sustainability of the scheme was 90.08%. During the study period the total effectivity of scheme infrastructure was 20.69%. It displayed that high system maintenance is required. Generally, the performance of the irrigation scheme is poor. Therefore, scheme monitoring, capacity building of the users and the water user associations, providing the flow control measurement structures, adequate operation and maintenance of the system are required to improve the irrigation scheme performance.