Afforestation of Degraded Croplands as a Water-Saving Option in Irrigated Region of the Aral Sea Basin

Navneet Kumar,John P. A. Lamers,Bernhard Tischbein,Asia Khamzina,Patrick Knöfel

doi:10.3390/w13101433

Navneet Kumar, John P. A. Lamers + Show 3 more

Open Access

https://doi.org/10.3390/w13101433

Copy DOI

Journal: Water	Publication Date: May 20, 2021
Citations: 11	License type: CC BY 4.0

Affiliation: University of Bonn, Korea University, University of Würzburg

Abstract

Climate change is likely to decrease surface water availability in Central Asia, thereby necessitating land use adaptations in irrigated regions. The introduction of trees to marginally productive croplands with shallow groundwater was suggested for irrigation water-saving and improving the land’s productivity. Considering the possible trade-offs with water availability in large-scale afforestation, our study predicted the impacts on water balance components in the lower reaches of the Amudarya River to facilitate afforestation planning using the Soil and Water Assessment Tool (SWAT). The land-use scenarios used for modeling analysis considered the afforestation of 62% and 100% of marginally productive croplands under average and low irrigation water supply identified from historical land-use maps. The results indicate a dramatic decrease in the examined water balance components in all afforestation scenarios based largely on the reduced irrigation demand of trees compared to the main crops. Specifically, replacing current crops (mostly cotton) with trees on all marginal land (approximately 663 km2) in the study region with an average water availability would save 1037 mln m3 of gross irrigation input within the study region and lower the annual drainage discharge by 504 mln m3. These effects have a considerable potential to support irrigation water management and enhance drainage functions in adapting to future water supply limitations.

Highlights

Climate change predictions for Central Asia point to a probable increase in atmospheric temperature coupled with a decrease in precipitation [1], which stipulate an increase in annual evapotranspiration [2]
Considering the land use changes in afforestation scenarios based on the land use map of 2005, the “100% afforestation” scenario would result in approximately 438 km2 (10.8%) of cotton land converted to tree plantation under average water availability conditions whereas only 263 km2 (6.5%) of the land would be afforested in the “62% afforestation” scenario (Figure 8)
The Soil and Water Assessment Tool (SWAT) modeling results indicated a dramatic decrease in the examined water balance components (i.e., GWQ, percolation, actual evapotranspiration (AET), soil moisture, and water yield) in afforestation scenarios considering both low and average water availability for irrigation

Summary

Introduction

Climate change predictions for Central Asia point to a probable increase in atmospheric temperature coupled with a decrease in precipitation [1], which stipulate an increase in annual evapotranspiration [2]. These changes are likely to reduce crop yields by as much as 30% and cause substantial economic losses in this region, which is highly dependent on irrigated agriculture [3]. The other major concern that is likely to worsen owing to climate change is cropland degradation and yield declines resulting from soil salinization The latter is rampant in the downstream countries, affecting approximately 50% of irrigated land in Uzbekistan and. Experiences in drylands elsewhere emphasize the role of tree plantations as a low-cost measure in improving salt balances by controlling elevated water tables in agricultural regions at both the farm and regional scales [16,17]

Methods

Results

Discussion

Conclusion