Designing on-farm irrigation ponds for high and stable yhield for different climates and risk-coping attitudes

Authors: VICO, GIULIA - Swedish University Of Agricultural Sciences; TAMBURINO, LUCIA - Swedish University Of Agricultural Sciences; Rigby Jr, James

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2020
Publication Date: 5/1/2020
Citation: Vico, G.R., Tamburino, L., Rigby Jr, J.R. 2020. Designing on-farm irrigation ponds for high and stable yhield for different climates and risk-coping attitudes. Journal of Hydrology. 584(2020)124634. https://doi.org/10.1016/j.jhydrol.2020.124634.

Interpretive Summary: Reservoirs have been advocated for storing water on farms to reduce dependence on groundwater and improve the sustainability of irrigated agriculture in the Mississippi River Alluvial Plain. The construction of reservoirs often requires taking some land out of crop production, thus farmers want reservoirs to be as small as possible. In order to minimize the size of reservoirs, ARS researchers modeled the operation of reservoirs for capturing rainfall and supplying water for corn irrigation under current and altered climate scenarios to evaluate the risk of having too little water during the growing season if farmers depended solely on reservoirs for irrigation. This work shows that for increasingly warmer climates farmer's will have two choose between designing reservoirs in order either to maximize yield or meet a stable acceptable annual yield as these two goals diverge under climatic pressure. Future work will analyze the optimal portfolio of irrigation options including both surface and ground water sources.

Technical Abstract: In many regions precipitation does not reliably meet crop water demands – a situation that climate change will likely exacerbate. Supplemental irrigation can help enhance and stabilize crop yields, but the need of water for irrigation has often led to groundwater over-exploitation. On-farm ponds can provide a more sustainable water source. Their use has often been promoted by local authorities, but, by converting a portion of cultivated area to water storage and reducing water availability downstream, on-farm ponds also imply constraints and trade-offs. For an effective exploitation of their potential benefits, they must be carefully designed and managed based on the local edaphic and climate conditions – a non trivial, task because of the cascading effects of rainfall unpredictability. Here we identify the most suitable on-farm pond size, according to two criteria: maximization of average yield (i.e., production maximization) and achievement of a minimum acceptable yield (i.e., risk minimization, accounting for the farmer’s risk aversion). To this aim, we develop a minimalist model, requiring few, physically based parameters, coupling crop biomass, soil moisture, and water stored in the pond. While general, the model is here applied to a case-study in the Lower Mississippi River Basin (USA). Simulations show that yield maximization and risk minimization are goals hard to reconcile, regardless of climatic conditions, soil type and irrigation strategy, with smaller ponds allowing the maximum average yield at the cost of reducing its stability from year to year. Stress avoidance irrigation ensures higher yields than deficit irrigation, even if it implies a faster use of the stored water. Future, more extreme climates will result in lower maximum average yields and narrower ranges of pond sizes ensuring desirable minimum yields.