Although most recharge estimation studies apply multiple methods to identify the possible range in recharge values, many do not distinguish clearly enough between inherent uncertainty of the methods and other factors affecting the results. We investigated the additional value that can be gained from multi‐method recharge studies through insights into hydrogeological understanding, in addition to characterizing uncertainty. Nine separate groundwater recharge estimation methods, with a total of 17 variations, were applied at a shallow aquifer in northwest Ethiopia in the context of the potential for shallow groundwater resource development. These gave a wide range of recharge values from 45 to 814 mm/a. Critical assessment indicated that the results depended on what the recharge represents (actual, potential, minimum recharge or change in aquifer storage), and spatial and temporal scales, as well as uncertainties from application of each method. Important insights into the hydrogeological system were gained from this detailed analysis, which also confirmed that the range of values for actual recharge was reduced to around 280‐430 mm/a. This study demonstrates that even when assumptions behind methods are violated, as they often are to some degree especially when data are limited, valuable insights into the hydrogeological system can be gained from application of multiple methods.

A field experiment consists of conservation agriculture (CA) and conventional tillage (CT) practices were set up in two areas, Robit and Dangishta, in sub-humid Ethiopian highlands. Irrigation water use, soil moisture, and agronomic data were monitored, and laboratory testing was conducted for soil samples, which were collected from 0 to 40 cm depth before planting and after harvest during the study period of 2015–2017. Calculation of crop coefficient (Kc) revealed a significant decrease in K_c values under CA as compared to CT. The result depicted that CA with a drip irrigation system significantly (α = 0.05) reduced K_c values of crops as compared to CT. Specifically, 20% reductions were observed for onion, cabbage, and garlic under CA whereas 10% reductions were observed for pepper throughout the crop base period. Consequently, irrigation water measurement showed that about 18% to 28% of a significant irrigation water savings were observed for the range of vegetables under CA as compared to CT. On the other hand, the results of soil measurement showed the CA practice significantly (α = 0.05) increased soil moisture (4%, 7%, 8%, and 10% increment for onion, cabbage, garlic, pepper) than CT practice even if irrigation input was small in CA practice. In addition, CA was found to improve the soil physico-chemical properties with significant improvement on organic matter (10%), field capacity (4%), and total nitrogen (10%) in the Dangishta experimental site. CA with drip irrigation is evidenced to be an efficient water-saving technology while improving soil properties to support sustainable intensification in the region.

This study was conducted at the Dangishta watershed in the Ethiopian highlands to evaluate irrigation potential from surface and groundwater sources under different farming and water application systems. Daily streamflow and the groundwater table were monitored from 2015 to 2017. Shallow groundwater recharge was estimated using the water table fluctuation method. Automated baseflow separation techniques were used to determine the amount of runoff and baseflow from the total streamflow records. The potential of groundwater and runoff to sustain dry season irrigation (i.e., low flow) was evaluated considering two tillage systems (i.e., conservation agriculture, CA; and conventional tillage, CT), and water application (i.e., drip and overhead) systems for major irrigated crops (i.e., onion, garlic, cabbage, and pepper) grown in the Dangishta watershed. We found that the annual groundwater recharge varied from 320 to 358 mm during the study period, which was about 17% to 22% of the annual rainfall. The annual surface runoff depth ranged from 192 to 268 mm from 2015 to 2017. The results reveal that the maximum seasonal irrigable land from groundwater recharge was observed under CA with drip irrigation (i.e., 2251 and 2992 ha from groundwater recharge and surface runoff, respectively). By comparison, in the CT practice with overhead irrigation, the lowest seasonal irrigable land was observed (i.e., 1746 and 2121 ha from groundwater and surface runoff, respectively). From the low flow analysis, about 199 and 173 ha of one season’s irrigable land could be irrigated using the CA and CT systems, respectively, both with drip irrigation. Similarly, two-season overhead irrigation potential from low flow under CA and CT was found to be about 87 and 76 ha, respectively. The dry season irrigable land using low flow could be increased from 9% to 16% using the CA system for the various vegetables, whereas drip irrigation could increase the irrigable land potential by 56% compared to overhead irrigation. The combined use of groundwater recharge and runoff could sustain up to 94% of the dry season low flow irrigation through the combination of the CA system and drip irrigation. Decision makers must consider the introduction of feasible and affordable technologies to make use of groundwater and direct runoff, to maximize the potential of dry season production through efficient and appropriate CA and water management practices.

Small-scale irrigation in Ethiopia is a key strategy to improve and sustain the food production system. Besides the use of surface water for irrigation, it is essential to unlock the groundwater potential. It is equally important to use soil management and water-saving systems to overcome the declining soil fertility and the temporal water scarcity in the region. In this study, the solar MajiPump was introduced to enable dry season crop production in Ethiopia using shallow groundwater sources. The capacity of the MajiPumps (MP400 and MP200) was tested for the discharge head and discharge using three types of solar panels (150 W and 200 W rigid, and 200 W flexible). Besides, drip irrigation and conservation agriculture (CA) farming systems were evaluated in terms of water productivity and crop yield in comparison to the farmers’ practice (overhead irrigation and tilled farming system). Results indicated that the maximum discharge head capacity of the MajiPumps was 18 m, 14 m, 10 m when using MP400 with 200 W rigid, MP400 with 200 W flexible, and MP200 with 150 W rigid solar panels, respectively. The corresponding MajiPump flow rates ranged from 7.8 L/min to 24.6 L/min, 3 L/min to 25 L/min, and 3.6 L/min to 22.2 L/min, respectively. Compared to farmer’s practice, water productivity was significantly improved under the CA farming and the drip irrigation systems for both irrigated vegetables (garlic, onion, cabbage, potato) and rainfed maize production. The water productivity of garlic, cabbage, potato, and maize was increased by 256%, 43%, 53%, and 9%, respectively, under CA as compared to conventional tillage (CT) even under overhead irrigation. Thus, farmers can obtain a significant water-saving benefit from CA regardless of water application systems. However, water and crop productivity could be further improved in the combined use of MajiPump with CA and drip irrigation (i.e., 38% and 33% water productivity and 43% and 36% crop productivity improvements were observed for potato and onion, respectively). Similarly, compared to CT, the use of CA significantly increased garlic, cabbage, potato, and maize yield by 170%, 42%, 43%, and 15%, respectively under the MajiPump water-lifting system. Overall, the solar-powered drip irrigation and CA farming system were found to be efficient to expand small-scale irrigation and improve productivity and livelihoods of smallholder farmers in Ethiopia.

Proper and reasonable estimation of actual evapotranspiration is critical for the design, operation, and management of irrigation systems. However, the density of climatic stations is low in many parts of Ethiopia to estimate spatially reasonable reference evapotranspiration (ETo), and the lack of spatial variability of crop coefficient (Kc) is clear barrier to the proper management of irrigation water. Therefore, the main objective of this study was to estimate reasonable crop evapotranspiration (ETc) by deriving spatially and temporally varying crop coefficients using remote sensing products in 10 wheat plots at the Koga irrigation scheme. The moderate-resolution imaging spectroradiometer (MODIS) potential evapotranspiration was calibrated at two class-I climate stations (Bahir Dar and Dangila) based on Penman–Monteith estimates and Normalized Difference Vegetation Index (NDVI) was derived from Sentinel 2B, which was later used to derive Kc. The correlation between reference evapotranspiration from MODIS Penman Monteith was acceptable for both Dangila (R² = 0.64) and Bahir Dar (R² = 0.74) stations. The MODIS calibration constant for Koga irrigation schemes was 0.27 and 1.99 (regression slope and constant) on an 8-day basis. Similarly, a strong correlation (R² = 0.95) was found between Sentinel-based NDVI and FAO crop coefficient, which indicated an alternative pathway for estimating crop coefficient. The value of Kc varies in space (across the 10 plots) from 0.16 to 0.42 at the initial stage and from 1.20 to 1.32 at the mid-stage. Similarly, the mean value of Kc varies in time from 0.29 at the initial stage to 1.26 at the mid-stage. On the other hand, evaluation of MODIS and WaPOR ETc found a significant difference (p < 0.05) with the calibrated MODIS-Sentinel 2B derived ETc. This indicated the need to calibrate both MODIS and WaPOR for the proper estimation of crop water needs. Underestimation of ET was observed from MODIS, and the reverse is true for WaPOR. Our findings showed that calibrating and integrating MODIS with Sentinel 2B would be a feasible approach to estimate Kc and hence ETc that varies in time and space. This would assist water managers in estimating crop water needs for better productivity in the region.

This study was conducted in the Abbay basin of Ethiopia to evaluate land suitability for irrigation considering both surface and groundwater sources using the analytic hierarchy process. Multiple factors which affect irrigated agriculture productivity were considered, and an 85% threshold was applied to identify irrigable land. The suitability result was validated using ground truth data from existing irrigation projects for surface water sources and depth to groundwater data for groundwater sources. The low flow potential of rivers, which is dependable for surface irrigation, was evaluated against suitable land considering the most dominant crops. The result showed that nearly 10% of the basin area (19 192 km ² ) and 5.3% of the basin (10 364 km ² ) were found suitable for surface irrigation from rivers and groundwater, respectively. South Gojam was found to be the most suitable sub-basin (approx. 3880 km ² ) for surface irrigation, whereas Muger was found to be the most suitable sub-basin (approx. 2105 km ² ) for surface irrigation from rivers and groundwater, respectively. Depth to groundwater was shallow for Muger as compared with other sub-basins. The validation result depicted more than 83% and 73% overlap for surface and groundwater sources, respectively. Land suitability and water availability assessment result in the Abbay basin shows a promising result for surface irrigation developments.