Effects of the shallow water table on water use of winter wheat and ecosystem health: Implications for unlocking the potential of groundwater in the Fergana Valley (Central Asia)

Abstract

a b s t r a c tThis paper analyzes the effect of the shallow water table on water use of the winter wheat (Triticum aestivum L.) that has replaced alfalfa (Medicago sativa) on the irrigated lands of the Fergana Valley, upstream of the Syrdarya River, in Central Asia. The effect of the shallow water table is investigated using HYDRUS-1D. Numerical simulations show that the contribution of the groundwater to evapotranspiration increases with a rising water table and decreases with increasing irrigation applications. Under irrigation conditions, an increase in the groundwater evapotranspiration is associated mainly with an increase in evaporation loss, causing a buildup of salinity in the crop root zone. Evaporation losses from fields planted with winter wheat after the harvest amount up to 45-47% of total evaporation thus affecting soil salinity and ecosystem health. Promoting the use of groundwater for irrigation in order to lower the groundwater table is suggested to achieve water savings from the change in the cropping pattern. Unlocking the potential of groundwater for irrigation in the Fergana Valley can also contribute toward managing soil salinity and improving the health and resilience of water, land and ecosystems of water, land and ecosystems (WLE).

Drought Tip: Use of Shallow Groundwater for Crop Production

“…Ayars et al (2006) summarize, for crops that have successfully used significant amounts of shallow groundwater, the soils in which they were grown, the water table depths and salinity, and the irrigation management and associated climate conditions (e.g., average rainfall). Additional studies not included in the table in Ayars et al (2006) that have similar results as those tabulated include those for sudangrass and alfalfa hay crops (Bali et al 2001a and2001b;Grismer and Bali 2001;Grismer et al 2001), as well as corn (Kang et al 2001), winter wheat (Kang et al 2001;Karimov et al 2014), safflower (Gharmarnia et al 2011), and date palm trees (Zeineldin 2010). …”

Simulation of Water Use Dynamics by Salix Bush in a Semiarid Shallow Groundwater Area of the Chinese Erdos Plateau

“…Nevertheless, quantifying groundwater use is another issue. The contribution of groundwater to vegetation water use varies by crop [46], grass [47], and trees [39] according to the Richards equation. However, these studies did not consider the effect of thermal driving flow.…”

Can a change in cropping patterns produce water savings and social gains: A case study from the Fergana Valley, Central Asia

“…He et al (2017) further used HYDRUS-1D to simulate the irrigated winter wheat/summer maize rotation system in the North China Plain for a total of 15 years. One of the advantages of the model for our study is that it provides estimates of upward fluxes from a shallow groundwater table during deficit irrigation (e.g., Karimov et al, 2014).…”

“…Managing the irrigation demand by reducing the beneficial use in agriculture may not always bring real water savings (Ward and Pulido-Velazquez, 2008). It may result in lowering the productivity of the use of thermal and land resources, affecting instream use values (Ward and Booker, 2003), increasing salinity (Khan and Hanjra, 2008), and negatively impacting ecosystem health (Karimov et al, 2014), but it may also deliver other socioeconomic benefits including incomes, employment, revenue, and gains in food security (Molden et al, 2010) for both rural and urban consumers. This highlights the necessity to quantitatively assess the impact of cropping changes beyond land and water savings and to consider also other social gains to the wider public.…”