Adaptive agricultural water resources management in a desert river basin: Insights from hydrologic modeling

Many arid and semi-arid areas around the world are projected to experience increasing aridity levels throughout the 21st century. The increase in the frequency and severity of droughts and changing precipitation patterns will likely intensify the water shortages. The widening gap between water availability and demand in arid and semi-arid areas necessitates better understanding of water quantity and quality issues in these regions. The objectives of this dissertation are: (1) reviewing the challenges of applying soil and water assessment tool (SWAT) watershed hydrology and water quality model in arid/semi-arid regions with irrigated agriculture; (2) robust analysis of water availability in an example desert river basin under plausible future climate conditions; and (3) evaluating water and land management interventions for adaptive water resources management and agricultural water sustainability. The results show the possibility of dryer future and more saline water resources, increasing the risks of crop loss, especially for high-value crops like pecan. The current agricultural water management practices that support growing pecan orchards will be difficult to implement in the future due to growing water shortages. It is timely for agricultural producers to develop preparedness to use water with marginal quality or take action to reduce the net consumptive water use of their operations by improving agricultural water management. Changing the crop pattern and applying deficit irrigation for water intensive crops like alfalfa helps reduce the irrigation water consumption while growing more drought resistant crops such as pistachio and pomegranate could improve the resilience of agricultural producers to long-term droughts. Challenges of modeling agricultural watersheds in arid/semi-arid regions are addressed in this dissertation to provide a technical road map for watershed modelers interested in applying SWAT

Agro-hydrological modelling of regional irrigation water demand

The irrigation sector accounts for over 70% of the total freshwater consumption in the world. Therefore, e cient management of irrigation water is essential to ensure water, food, energy and environmental securities in a sustainable manner; these securities are grand challenges of the 21st century. The main objective of this research is to evaluate the simulation of irrigation water demand at the catchment scale in order to develop improved tools for conducting quantitative planning and climate change studies. Irrigation water demand is mostly driven by soil moisture. It is a state variable which is used to trigger the irrigation in hydrological models. In this study, a hydrolgical model (Soil and Water Assessment Tool, SWAT) is evaluated for reliably simulating the spatial and temporal patterns of soil moisture at a catchment scale. The SWAT simulated soil moisture was compared with the indirect estimates of soil moisture from Landsat and Time-domain re ectometry (TDR). The results showed that the SWAT simulated soil moisture was comparable with the soil moisture estimated from Landsat and TDR. Secondly, the applicability of the SWAT model was tested for simulating stream ow, evapotranspiration (ET) and irrigation water demand for four di erent agro-climatic zones (Mediterranean, Subtropical monsoon, Humid, and Tropical). Two di erent irrigation scheduling techniques were used to simulate irrigation namely, soil water de cit and plant water demand. It was seen from the results that the SWAT simulated irrigation amounts under soil moisture irrigation scheduling technique were close to the irrigation statistics provided by the state. However, the irrigation amounts simulated under the plant water demand irrigation scheduling technique were underestimated. Additionally, the two reanalysis data were also used to check the data uncertainty in simulating irrigation water demand. SWAT model code was modi ed by incorporating modi ed root density distribution function and dynamic stress factor. The modi ed model was used to simulate irrigation and crop yield. It was tested against the irrigation and crop yield simulated by Soil Water Atmosphere Plant (SWAP) model and eld data (Hamerstorf, Lower Saxony, Germany). It was then validated for di erent catchments (Germany, India and Vietnam). The results showed that the SWAT simulated irrigation water demand in case of plant water demand is comparable with the amount simulated by the model under soil water de cit irrigation scheduling technique. This dissertation not only bridges the gap between the scales of soil moisture determination but also establishes a close connection with the actual observations and modelled soil moisture and irrigation amounts at the eld, regional and global studies in agricultural water management. Additionally, the studies about simulating irrigation water requirement in data-scarce areas must address data uncertainty when using reanalysis data. It was found that rainfall is not always the dominant variable in irrigation simulation. Therefore, it is worth checking and bias correct the other climate variables

Друга міжнародна конференція зі сталого майбутнього: екологічні, технологічні, соціальні та економічні питання (ICSF 2021). Кривий Ріг, Україна, 19-21 травня 2021 року

Second International Conference on Sustainable Futures: Environmental, Technological, Social and Economic Matters (ICSF 2021). Kryvyi Rih, Ukraine, May 19-21, 2021.Друга міжнародна конференція зі сталого майбутнього: екологічні, технологічні, соціальні та економічні питання (ICSF 2021). Кривий Ріг, Україна, 19-21 травня 2021 року