Estimating Surface and Groundwater Irrigation Potential under Different Conservation Agricultural Practices and Irrigation Systems in the Ethiopian Highlands

Abstract

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.

Evaluating land suitability and water availability for surface irrigation in the Abbay basin of Ethiopia

“…NIR = 1.6 × Kc × ETo – ER,where NIR, Kc, ETo and ER are net irrigation requirement (mm), crop coefficient (dimensionless), reference evapotranspiration (mm) and effective rainfall (mm), respectively. The coefficient 1.6 behind Kc was introduced to account for the inefficacy of surface irrigation due to water application losses, conveyance losses, losses for land preparation and leaching [55]. Details of surface irrigation losses in the region can be referred from Belay et al .…”

“…A total of 15 river gauging stations were considered. The low flow volume (90 percentile flow) of rivers was considered to compute the potentially irrigable land from rivers [ 55 ]. Low flow volume was divided by the net irrigation requirement of crops dominantly grown in the Abbay basin (sorghum, wheat and maize) [ 19 ], using equation (3.3) to get the potentially irrigable land from rivers without the need for storage structure.…”

“…In the second stage, the land suitability evaluation result was validated using information from shallow groundwater wells (depth) and currently irrigated lands from rivers. In the third stage, a case study was conducted to evaluate the potential of main rivers to address suitable land for irrigation considering the irrigation requirements of dominant crops grown in the basin, and the low flow (90 percentile flow) of rivers based on Yimam et al [55].…”

“…In the third stage, a case study was conducted to evaluate the potential of main rivers to address suitable land for irrigation considering the irrigation requirements of dominant crops grown in the basin, and the low flow (90 percentile flow) of rivers based on Yimam et al . [55].

Figure 2Framework to identify suitable land for irrigation from surface and groundwater (GW).

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Spatial and Temporal Changes in Wetland in Dongting Lake Basin of China under Long Time Series from 1990 to 2020

“…Generally, in the past 30 years, forest land mainly contributed to the growth of the river plus canal, accounting for 58.49% of the total net increase in wetlands. On the one hand, the river-plus-canal areas were important water conservancy facilities for the development of agriculture [26]. Simultaneously, with the improvement in people's living standards, there was a growing demand for varieties of crop species, which led to the development of suburban agriculture, thus occupying a part of the wetland.…”