Post-processing R tool for SWAT efficiently studying climate change impacts on hydrology, water quality, and crop growth

Authors: DING, BEIBEI - China Agricultural University; LIU, HAIPENG - China Agricultural University; LI, YINGXUAN - China Agricultural University; ZHANG, XUELIANG - China Agricultural University; FENG, PUYU - China Agricultural University; LI LIU, DE - University Of New South Wales; Marek, Gary; ALE, SRINIVASULU - Texas A&M Agrilife; Brauer, David; SRINIVASAN, RAGHAVAN - Texas A&M University; CHEN, YONG - China Agricultural University

Submitted to: Environmental Modelling & Software
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2022
Publication Date: 8/20/2022
Citation: Ding, B., Liu, H., Li, Y., Zhang, X., Feng, P., Li Liu, D., Marek, G.W., Ale, S., Brauer, D.K., Srinivasan, R., Chen, Y. 2022. Post-processing R tool for SWAT efficiently studying climate change impacts on hydrology, water quality, and crop growth. Environmental Modelling & Software. 156. Article 105492. https://doi.org/10.1016/j.envsoft.2022.105492.
DOI: https://doi.org/10.1016/j.envsoft.2022.105492

Interpretive Summary: Climate change is expected to present additional strain on agricultural crop production systems throughout the world. Increased irrigation requirements associated with elevated temperatures and CO2 concentrations may exacerbate the decline of the Ogallala Aquifer in the Southern High Plains (SHP). Although future climate conditions are uncertain, the use of multiple global circulation models (GCM) and representative concentration pathways (RCP) provide a range of possible scenarios. Coupled with simulation modeling, data from climate change scenarios may aid in the development of alternative crop management strategies that maintain profitability and extend groundwater resources in the SHP. Researchers from China Agricultural University, USDA-ARS Bushland, and Texas A&M University evaluated irrigated and dryland cotton production under 27 future climate scenarios using a post processing. Changes in water balance components, total nitrogen load, and crop growth characteristics from a watershed scale simulation were evaluated for the middle and end of the 21st century. Results showed that dryland and irrigated cotton lint yields may increase by 46-86 percent and 92-124 percent, respectively under most climate change models. These findings suggest that cotton may be a viable option for the SHP under expected climate change conditions under both dryland and deficit irrigation management.

Technical Abstract: To arrange crop planting and formulate adaptive policies for climate change, the effects of future climate on hydrology, water quality, and crop production need to be evaluated on a watershed scale. This study developed a post-processing R tool for processing SWAT (Soil and Water Assessment Tool) output results driven by long-term climate data, including outputs of different time scales of yearly, monthly, and daily. A case study was performed in the Double Mountain Fork Brazos watershed in the Texas Panhandle using the R tool. This study assessed the future changes in water balance components, total nitrogen load, and crop growth characteristics over the watershed in the middle and end of the 21st century with reference to the baseline period (1981-2010). The results of the study showed that the average annual irrigation amount in the cotton area slightly increased in the mid-21st century under SSP2-4.5 and SSP5-8.5 and 2071-2100 SSP2-4.5 scenarios. However, the average annual irrigation amount under the SSP5-8.5 scenario decreased by 17.5 percent in the late 21st century. A similar pattern was observed with ETa in irrigated cotton areas, while ETa showed a decreasing trend under all scenarios in dryland cotton areas. The average annual surface runoff increased by 8.9-17.9 mm and 11.5-22.6 mm in the irrigated and dryland cotton areas, respectively. Similar to the surface runoff, the total nitrogen load indicated an increasing trend in the future. The total nitrogen load in irrigated and dryland cotton areas in the mid-21st century increased about 0.4-0.6 kg/ha and 1.9-2.3 kg/ha. At the end of the 21st century, the irrigated cotton area and the dryland cotton area were about 0.4-0.9 kg/ha and 2.0-2.4 kg/ha, respectively. Compared with the historical period, the yields of irrigated and dryland cotton increased by 92.1-124.1 percent and 45.5-85.6 percent under the future climate scenarios, respectively. The study provides useful tools and information for soil and water conservation in the Texas Panhandle and can help formulate countermeasures to mitigate the negative impacts of future climate change on a watershed scale.