Optimizing Agricultural Water Use: A Comparative Analysis of Soil Moisture and Evapotranspiration-Based Irrigation Scheduling for Carrot Crop (Daucus Carota)

Melkamu Ateka Derebe, Ligalem Agegn Asres, Babur Tesfaye Yersaw — Tue, 28 Oct 2025 14:58:47 +0300

Crop production in Ethiopia is limited owing to water scarcity. Various technologies and management options are being used for efficient use of the available water resources in crop production. This study evaluated the performance of Soil Moisture (SM) and Evapotranspiration (ET) based irrigation scheduling methods on carrot yield and Water Use Efficiency (WUE), Water Productivity (WP) and field water use efficiency at water scarce areas of Arba Minch for two consecutive years/seasons of 2021 and 2022. The experimental design was a randomized complete block with three replicates. The treatments combined two scheduling techniques (soil moisture, SM, and evapotranspiration, ET). Water was delivered to furrows using an RBC flume, and data was analyzed with ANOVA at 5% significance level using SAS software and the graphs were drawn by Python. Across 2021 and 2022 seasons, SM-based irrigation consistently required less water than ET-based scheduling, achieving 5–5.4% water savings at full irrigation levels without reducing yields. Under moderate deficit irrigation (50–75%), both methods sustained comparable yields (42–43 t/ha), but SM-based treatments showed higher WUE, FWUE, and WP, with peak values at SM50% (WUE = 31.4 kg/m³; FWUE = 22.7 kg/m³; WP = 1.78 kg/m³) compared to ET50% (WUE = 25.8 kg/m³; FWUE = 18.1 kg/m³; WP = 1.78 kg/m³). Severe deficit irrigation (25%) drastically reduced yield and all efficiency indices in both methods. Economic analysis indicated that moderate irrigation levels (50%) maximized net benefits and cost-benefit ratios. Overall, SM-based irrigation was more efficient in water use, improved yield stability, and enhanced WUE, FWUE, and WP across irrigation levels. Thus, it demonstrated its suitability for sustainable carrot production under limited water resources. This saving is particularly relevant for Ethiopia where water scarcity limits crop production. It demonstrates a practical strategy for farmers to grow more food with less water while supporting sustainable resource management.

Keywords: Soil moisture; Furrow Irrigation; Crop evapotranspiration; ET-Based irrigation; SM-based irrigation

Evaluation of Koka Reservoir Operation under Sedimentation: Implications for Irrigation Water Demands in Upper Awash Valley, Awash River Basin

Habtamu Nemera — Mon, 10 Nov 2025 15:41:33 +0300

Water scarcity has been a major issue in the Awash River Basin of Ethiopia. The Koka Reservoir is the sole water storage source supporting extensive irrigation activities in the Upper Awash Valley, a key part of the basin. However, sedimentation has reduced the reservoir’s active storage capacity, posing serious risks to its ability to meet irrigation demands in the valley. This study aims to evaluate the reservoir’s operational performance by assessing irrigation water demand and analyzing the water supply-demand balance under recent sedimentation conditions. Key datasets include crops, census, digital elevation model, hydro-meteorological, and reservoir operation data. The primary software tools applied were CROPWAT, ArcMap, and HEC-ResSim. Water resource system performance evaluation criteria such as reliability, vulnerability, and resilience were employed. The annual estimated gross irrigation water requirement for the study region was 1,525 Mm³. Reservoir operation has been simulated using three decades of daily inflow from 1985 to 2015 by considering different alternatives of the irrigation water demands. When the model was simulated for Alternative 1, the reservoir met full demand less than half the time (time reliability 42.7%), supplied most of the total demand volume despite shortages (volumetric reliability 73.7%), experienced severe deficits when failures occurred (mean vulnerability 25.4 m³/s, maximum 80.0 m³/s), and had limited ability to recover (resilience 27.7%); even in Alternative 2, reliability and resilience improved and vulnerability was moderate, but full demand was still not consistently met. The results indicate that the reservoir capacity under recent sedimentation conditions is insufficient to store high inflows and meet high demand during rainy and dry seasons, respectively. This study does not account for the potential impacts of land use/land cover and climate change, which could influence the hydrological balance and reservoir performance.

Keywords: Awash River; CROPWAT; HEC-ResSim; Performance Evaluation; Reservoir Operation; Water Scarcity.

Ethiopian Journal of Water Science and Technology

Optimizing Agricultural Water Use: A Comparative Analysis of Soil Moisture and Evapotranspiration-Based Irrigation Scheduling for Carrot Crop (Daucus Carota)

Evaluation of Koka Reservoir Operation under Sedimentation: Implications for Irrigation Water Demands in Upper Awash Valley, Awash River Basin