Tag: irrigation systems
Stochastic impact evaluation of an irrigation development intervention in Northern Ethiopia
Irrigation plays a significant role in achieving food and nutrition security in dry regions. However, detailed ex-ante appraisals of irrigation development investments are required to efficiently allocate resources and optimize returns on investment. Due to the inherent system complexity and uncertain consequences of irrigation development interventions coupled with limited data availability, deterministic cost-benefit analysis can be ineffective in guiding formal decision-making. Stochastic Impact Evaluation (SIE) helps to overcome the challenges of evaluating investments in such contexts. In this paper, we applied SIE to assess the viability of an irrigation dam construction project in northern Ethiopia. We used expert knowledge elicitation to generate a causal model of the planned intervention’s impact pathway, including all identified benefits, costs and risks. Estimates of the input variables were collected from ten subject matter experts. We then applied the SIE tools: Monte Carlo simulation, Partial Least Squares regression, and Value of Information analysis to project prospective impacts of the project and identify critical knowledge gaps. Model results indicate that the proposed irrigation dam project is highly likely to increase the overall benefits and improve food and nutrition status of local farmers. However, the overall value of these benefits is unlikely to exceed the sum of the investment costs and negative externalities involved in the intervention. Simulation results suggest that the planned irrigation dam may improve income, as well as food and nutrition security, but would generate negative environmental effects and high investment costs. The Stochastic Impact Evaluation approach proved effective in this study and is likely to have potential for evaluating other agricultural development interventions that face system complexity, data scarcity and uncertainty.
Data for the evaluation of irrigation development interventions in Northern Ethiopia
This data article provides the datasets that are used in the holistic ex-ante impact evaluation of an irrigation dam construction project in Northern Ethiopia [1]. We used an expert knowledge elicitation approach as a means of acquiring the data. The data shared here captures all the parameters considered important in the impact pathway (i.e. the expected benefits, costs, and risks) of the decision to construct an irrigation dam. The dataset is disaggregated for two impact pathway models: one complementing the dam construction with catchment restoration and the other without catchment restoration. Both models are scripted in the R programming language. The data can be used to examine how the construction of an irrigation dam affects the incomes as well as the food and nutritional status of farmers that are affected by the intervention.
Viability of an Irrigation Development Intervention in Tigray: an Application of Stochastic Impact Evaluation
Assessing the feasibility of an irrigation daminvestment and optimizing expected returnsrequire detailed ex-ante appraisal.• Due to the inherently complex and uncertainconsequences of irrigation dam investmentsand often severe data scarcity, traditional costbenefitassessment methods face limitations.• Stochastic Impact Evaluation (SIE; Luedelingand Shepherd 2016) attempts to overcome theparticular challenges of evaluating investmentsin such contexts.
Resilience Diagnostic and Decision Support Tool
Exploring optimal farm resources management strategy for Quncho-teff (Eragrostis tef (Zucc.) Trotter) using AquaCrop model
Teff is a major staple food crop in Ethiopia. Moisture and soil fertility are the two major factors limiting teff yield. Studies were conducted across three sites in Ethiopa [Mekelle (MK) in 2012 and 2016, Ilala (IL) in 2012 and Debrezeit (DZ) in 2009 and 2010]. The objectives of these studies were (1) to assess the response of Quncho-teff to different fertilizer and irrigation levels; 2) to quantify irrigation water productivity (IWP), and (3) to collect data to calibrate and validate AquaCrop model for simulating yield and evaluate optimal irrigation and sowing date strategy for Quncho-teff at different locations in Ethiopia. The different fertilizer levels were: 1) 64 kg N and 46 kg P/ha (N2P2); 2); 32 kg N and 23 kg P/ha (N1P1); 3) 0 kg N and 0 kg P/ha (N0P0) and 4) 52 kg N and 46 kg P/ha (N3P3). The four irrigation treatments were: zero (rainfed), two, four and full irrigation applications. Findings showed that full irrigation in combination with high fertilizer (N2P2) could give better yield. However, during abnormal rainfall, spreading the available fertilizer at a rate of 32 kg N and 23 kg P/ha may be preferable to applying 64 kg N and 46 kg P/ha. This study also indicated that the regional fertilizer recommendations for teff need to be revised taking in to account the soil characteristics, climate and irrigation water availability. The AquaCrop model was able to simulate the observed canopy cover, soil water, biomass and yield of teff satisfactorily. Canopy cover was simulated with normalized root mean square error (NRMSE), index of agreement (I) and R2 of 7%, 0.5 and 0.8, respectively. Soil moisture during the season was simulated with NRMSE of 11.4–15.7%, I of 0.99 and R2 of 0.85–0.9. Simulated final aboveground biomass values were in close agreement with the measured (NRMSE, 7.8%, I, 0.89 and R2, 0.66). There was also good agreement between simulated and measured grain yield with NRMSE, I and R2 values of 10.9%, 0.93, 0.80, respectively. Scenario analysis indicated that early sowing was the best option to maximize teff yield with the least amount of irrigation. Scenario analysis also showed that one irrigation during flowering stage could substantially improve irrigation water productivity (IWP) of teff and minimize the yield loses which could occur due to shifting of sowing date from early to normal. Two irrigation applications also substantially improved the yield and IWP of late sown teff. However, to get high yield, a late sown teff should receive at least four irrigation applications during the mid-growth stage of the crop. These results suggest that AquaCrop model can be used to identify optimal farm resource management strategies for teff production. © 2016
Sensitivity of groundwater recharge under irrigated agriculture to changes in climate, CO2 concentrations and canopy structure
Estimating groundwater recharge in response to increased atmospheric CO2 concentration and climate change is critical for future management of agricultural water resources in arid or semi-arid regions. Based on climate projections from the Intergovernmental Panel on Climate Change, this study quantified groundwater recharge under irrigated agriculture in response to variations of atmospheric CO2 concentrations (550 and 970 ppm) and average daily temperature (+1.1 and +6.4 C compared to current conditions). HYDRUS 1D, a model used to simulate water movement in unsaturated, partially saturated, or fully saturated porous media, was used to simulate the impact of climate change on vadose zone hydrologic processes and groundwater recharge for three typical crop sites (alfalfa, almonds and tomatoes) in the San Joaquin watershed in California. Plant growth with the consideration of elevated atmospheric CO2 concentration was simulated using the heat unit theory. A modified version of the Penman-Monteith equation was used to account for the effects of elevated atmospheric CO2 concentration. Irrigation amount and timing was based on crop potential evapotranspiration. The results of this study suggest that increases in atmospheric CO2 and average daily temperature may have significant effects on groundwater recharge. Increasing temperature caused a temporal shift in plant growth patterns and redistributed evapotranspiration and irrigation water use earlier in the growing season resulting in a decrease in groundwater recharge under alfalfa and almonds and an increase under tomatoes. Elevating atmospheric CO2 concentrations generally decreased groundwater recharge for all crops due to decreased evapotranspiration resulting in decreased irrigation water use. Increasing average daily temperature by 1.1 and 6.4 C and atmospheric CO2 concentration to 550 and 970 ppm led to a decrease in cumulative groundwater recharge for most scenarios. Overall, the results indicate that groundwater recharge may be very sensitive to potential future climate changes.
Risks Associated with Urban Wastewater Irrigation and Production of Traditional African Vegetable (TAVs) Seeds in Nairobi, Kenya
Globally farmers use wastewater to irrigate crops because it also supplies plant nutrients and ensures all year round food availability. A study was carried out in Nairobi with farmers who used wastewater to produce both food and fodder along the Ngong/Motoine River to obtain an understanding of the benefits and risks associated with wastewater farming and to identify mitigation strategies. Farmers cultivated plots below 0.5 acres where they grew vegetables for home consumption, sale for employment. Analysis of the wastewater samples showed that heavy metal contents were within acceptable limits. However, investigation done on plant samples taken from selected crops showed that there was bioaccumulation of cadmium, chromium and lead to levels that were several times higher than the recommended critical limits. Determination of biological contamination samples from these farms and from the wet markets showed that produce from the markets had higher loads of faecal colifoms and parasitic eggs than vegetables irrigated with untreated water. One strategy for mitigating health risks associated with consumption of the contaminated vegetables was to introduce an alternative farming activity to farmers which in this case was to introduce production of Traditional African Vegetables seeds. Eight farmers have for two seasons been able to produce 30 kg of assorted seeds valued at KShs 30000 or USD 400. This has increased both income and assets for farming households and availability of quality seed for rural and urban farmers.
Farm size limits agriculture’s poverty reduction potential in Eastern India even with irrigation-led intensification
Millions of people living in the Eastern Gangetic Plains (EGP) of India engage in agriculture to support their livelihoods yet are income poor, and food and climate insecure. To address these challenges, policymakers and development programs invest in irrigation-led agricultural intensification. However, the evidence for agricultural intensification to lift farmers’ incomes above the poverty line remains largely anecdotal. The main objective of this study is to use a large household survey (n = 15,572; rice: 8244, wheat: 7328; 2017/18) to assess the link between agricultural intensification and personal daily incomes from farming (FPDI) in the rice-wheat systems of the EGP – the dominant cropping system of the region. We use the Intensification Benefit Index (IBI), a measure that relates farm size and household size to FPDI, to assess how daily incomes from rice-wheat production change with irrigation-led intensification across the EGP. Relative to the international poverty line of 1.90 Purchasing Power Parity (PPP)$ day−1 and accounting for variations in HH size in the analysis, we found that small farm sizes limit the potential for agricultural intensification from irrigation to transform the poverty status of households in the bottom three quartiles of the IBI. The estimated median FPDI of households with intensified systems in the bottom three quartiles is only 0.51 PPP$ day−1 (a 0.15 PPP$ gain). The median FPDI increases to 2.10 PPP$ day−1 for households in the upper quartile of the IBI distribution (a 0.30 PPP$ gain). Irrigation-led agricultural intensification of rice-wheat systems in the EGP may provide substantial benefits for resilience to climatic change and food security but achieving meaningful poverty reduction will require complementary investments. Transforming the poverty status of most smallholder farmers in the EGP requires diversified portfolios of rural on- and off-farm income-generating opportunities. While bolstering food- and climate security, agronomic intervention programs should consider smallholders’ limited monetary incentives to invest in intensification. Irrigation-led agricultural intensification programs and policies should explicitly account for the heterogeneity in household resources, irrigation levels, and degree of dependence on agricultural income.
Using biochar and deficit irrigation enhanced the growth of commercial agroforestry woody species seedlings in drylands (a case study in Saz, northern Ethiopia)
Water availability is the main challenge for the growth and development of woody species in drylands. Application of biochar under deficit irrigation can enhance seedling growth in arid regions. The growth of commercial woody species seedlings was monitored for approximately two years using the combined effect of biochar and deficit irrigation treatments. Biochar was applied to the plantation pits during plantation at a rate of 38 g kg−1 of soil. The applied deficit irrigation per season covered 60% (459 mm) and 35% (459 mm) of the dry season crop evapotranspiration for Citrus sinensis and Yushinia alpina, respectively. We found statistically clear effects of biochar and deficit irrigation on the growth of both species with combined application. Compared to control treatment, the combined application of biochar and deficit irrigation significantly (P < 0.05) increased new culms of Y. alpina by 44%. Moreover, the combined application of biochar and deficit irrigation significantly (P < 0.05) affected the height and diameter relative growth rates (RGRs) of both species by enhancing soil moisture and which in turn increased the photosynthesis and transpiration rates of the species. Compared to Y. alpina, C. sinensis had significantly (P < 0.05) higher height and diameter RGRs and higher transpiration rate. The maximum height RGRs of Y. alpina (0.142) and C. sinensis (0.108 cm month−1) were attained at the end of the rainy season. The highest and significant increment (266.5%) of biomass of Y. alpina was recorded in the plants subjected to combined application of biochar and deficit irrigation However, we could not confirm a significant effect of B alone on the growth parameters of the species. Hence, the integration of biochar and deficit irrigation would be essential for the successful establishment of C. sinensis and Y. alpina seedlings in farmlands of dried region.