Agricultural Water Productivity-Based Hydro-Economic Modeling for Optimal Crop Pattern and Water Resources Planning in the Zarrine River Basin, Iran, in the Wake of Climate Change

Abstract

For water-stressed regions/countries, like Iran, improving the management of agricultural water-use in the wake of climate change and increasingly unsustainable demands is of utmost importance. One step further is then the maximization of the agricultural economic benefits, by properly adjusting the irrigated crop area pattern to optimally use the limited amount of water available. To that avail, a sequential hydro-economic model has been developed and applied to the agriculturally intensively used Zarrine River Basin (ZRB), Iran. In the first step, the surface and groundwater resources, especially, the inflow to the Boukan Dam, as well as the potential crop yields are simulated using the Soil Water Assessment Tool (SWAT) hydrological model, driven by GCM/QM-downscaled climate predictions for three future 21th-century periods under three climate RCPs. While in all nine combinations consistently higher temperatures are predicted, the precipitation pattern are much more versatile, leading to corresponding changes in the future water yields. Using the basin-wide water management tool MODSIM, the SWAT-simulated water available is then optimally distributed across the different irrigation plots in the ZRB, while adhering to various environmental/demand priority constraints. MODSIM is subsequently coupled with CSPSO to optimize (maximize) the agro-economic water productivity (AEWP) of the various crops and, subsequently, the net economic benefit (NEB), using crop areas as decision variables, while respecting various crop cultivation constraints. Adhering to political food security recommendations for the country, three variants of cereal cultivation area constraints are investigated. The results indicate considerably-augmented AEWPs, resulting in a future increase of the annual NEB of ~16% to 37.4 Million USD for the 65%-cereal acreage variant, while, at the same time, the irrigation water required is reduced by ~38%. This NEB-rise is achieved by augmenting the total future crop area in the ZRB by about 47%—indicating some deficit irrigation—wherefore most of this extension will be cultivated by the high AEWP-yielding crops wheat and barley, at the expense of a tremendous reduction of alfalfa acreage. Though presently making up only small base acreages, depending on the future period/RCP, tomato- and, less so, potato- and sugar beet-cultivation areas will also be increased significantly.

Modeling the Impact of Climate Change on Water Availability in the Zarrine River Basin and Inflow to the Boukan Dam, Iran

“…The above predicted changes of the future inflow to the Boukan Dam, the major water supply reservoir in the ZRB, will have significant adverse implications on the water supply in the basin, requiring various adaptation strategies, especially, for agriculture, such as reduced or more efficient irrigation, or even changing the crop patterns, as has been indicated by e.g., Emami and Koch [40] for this agriculturally used basin in Iran.…”

“…It is predicted to have on average a slight increase which is more for RCP 4.5 (from 15% and 12% in validation and calibration periods to 17%, 16% and 15% in RCP 2.6, RCP 4.5 and RCP 8.5, respectively), as the liquid precipitation plus the snowmelt (denominator of the RC-ratio) will have a stronger reduction by 22% to 34% than the average surface runoff with only a 2%, 10% and 26% decrease for RCP 2.6, RCP 4.5 and RCP 8.5, respectively. Based on the values The above predicted changes of the future inflow to the Boukan Dam, the major water supply reservoir in the ZRB, will have significant adverse implications on the water supply in the basin, requiring various adaptation strategies, especially, for agriculture, such as reduced or more efficient irrigation, or even changing the crop patterns, as has been indicated by e.g., Emami and Koch [40] for this agriculturally used basin in Iran.…”

Sustainability Assessment of the Water Management System for the Boukan Dam, Iran, Using CORDEX- South Asia Climate Projections

“…More specifically, for the minimum and maximum temperatures, an additive correction constant CT j and for precipitation a multiplicative factor CP j , were employed. For further details, the readers are referred to studies by Emami and Koch [19,29].…”

Allocation of Groundwater Recharge Zones in a Rural and Semi-Arid Region for Sustainable Water Management: Case Study in Guadalupe Valley, Mexico

“…It is worth mentioning that the increase in temperature plays a crucial role, since it alters the availability of water and generally increases the intensity of droughts and their impacts. the population and the lack of sustainable management of water resources will pose a great challenge in the future to preserve food and water security [23]. A study by Gaeta-Lara [24] in 2006 projected an increase in the population with by an average annual rate of 2.08%; by 2030 this would cause a decrease in the available daily liters of water for each habitant from 90 L to 47 L.…”

“…Water 2019, 11, x FOR PEER REVIEW 3 of 17 challenge in the future to preserve food and water security [23]. A study by Gaeta-Lara [24] in 2006 projected an increase in the population with by an average annual rate of 2.08%; by 2030 this would cause a decrease in the available daily liters of water for each habitant from 90 L to 47 L. Particularly in the Guadalupe Valley, in the city of Ensenada, the development of diverse activities depends on the availability of the water stored in the aquifer and the intermittent flow in the streams of the Guadalupe Valley [25].…”