Significant impacts of irrigation water sources and methods on modeling irrigation effects in the ACMELand Model

Abstract

An irrigation module considering irrigation water source and irrigation method has been incorporated into the ACME Land Model (ALM). Global numerical experiments were conducted to investigate irrigation effects and their sensitivity to irrigation water sources and irrigation methods. All simulations shared the same irrigation soil moisture target constrained by a global census data set of irrigation amounts. Irrigation has large impacts on terrestrial water balances especially in regions with extensive irrigation. Such effects depend on the irrigation water source: surface water‐fed irrigation decreases runoff and water table depth, while groundwater‐fed irrigation increases water table depth, and increases or decreases runoff depending on the pumping intensity. Irrigation effects also depend significantly on the irrigation method. Flood irrigation applies water in large volumes within short durations, resulting in much larger impacts on runoff and water table depth than drip and sprinkler irrigation. Differentiating the irrigation water source and method is important not only for representing the distinct pathways of how irrigation influences the terrestrial water balances, but also for estimating irrigation water use efficiency. Specifically, groundwater pumping has lower irrigation water use efficiency than irrigation relying on surface water withdrawal only due to enhanced recharge rates. Different irrigation methods also affect water use efficiency, with drip irrigation being the most efficient followed by sprinkler and flood irrigation. Our results highlight the importance of explicitly accounting for irrigation source and irrigation method, which are the least understood and constrained aspects in modeling irrigation water demand, water scarcity, and irrigation effects in Earth System Models.

Memory of irrigation effects on hydroclimate and its modeling challenge

“…Levis et al 2012, Liu et al 2016, of human water-management modeling (e.g. Voisin et al 2017), and of irrigation methods (Leng et al 2017) in ESMs will accelerate the inclusion of more realistic irrigation-crop-water resource models and improve the representation of their interactions with weather and climate.…”

Irrigation enhances local warming with greater nocturnal warming effects than daytime cooling effects

“…To show the decrease in terrestrial water storage over the study area, which is related to the groundwaterfed irrigation, we used the Gravity Recovery and Climate Experiment Tellus monthly land water mass grids NetCDF release 5.0 [27] to analyze the seasonal land water storage change over the NCP (31…”

“…drip, sprinkler, and flood irrigation) and water source (i.e. surface water and groundwater) may have an effect on simulated results, however Leng et al [31] found that it can only affect the runoff and water table depth, and have no effect on evapotranspiration. Therefore, this study did not consider the different irrigation methods and water source.…”

Groundwater Withdrawals Under Drought: Reconciling GRACE and Land Surface Models in the United States High Plains Aquifer

“…To address this limitation, Leng et al (2014Leng et al ( , 2015 introduced a source water accounting scheme to CLM that withdraws water for irrigation in response to simulated irrigation applications. Like other efforts (Leng et al, 2017;Li et al, 2016;Mahalov et al, 2016;Ozdogan et al, 2010), irrigation applications in this formulation are demand-driven, and source water is withdrawn to meet the application required by the irrigation module. Because the model development was performed in CLM rather than a simplified GHM, Leng et al (2014Leng et al ( , 2015 were able to investigate local hydrological feedbacks influencing irrigation efficiency.…”