Satellite-Based Water Consumption Dynamics Monitoring in an Extremely Arid Area

Shen Tan,Bingfang Wu,Hongwei Zeng,Nana Yan

doi:10.3390/rs10091399

Abstract

Evapotranspiration (ET) involves actual water consumption directly from the land surface; however, regional ET maps are usually neglected during water management and allocation. In this study, an integrated satellite-based ET monitoring approach with two spatial resolutions is proposed over an extremely arid basin in China that has experienced crop area expansion and has been the focus of a water-saving project since 2012. The proposed ETWatch approach combined with an empirical downscaling strategy based on vegetation condition was employed to produce monthly ET maps. This method achieves satisfactory accuracy and is validated by its reasonable spatial and temporal pattern results. Yearly results exhibit an increasing ET trend before 2012, which subsequently gradually decrease. This trend fits well with the dynamics of the basin-wide vegetation condition, indicating that there is a stronger correlation between water consumption and vegetation than between other environmental indicators. The average ET over three main crop types in the region (grape, cotton, and melon) decreased by approximately 5% due to optimizations of the irrigation timeline during the project, while 13% of the water savings can be attributed to the fallowing of crop areas. Based on the irrigation distribution in 2012, a comparison between drip and border irrigation that achieves water savings of 3.6% from grape and 5.8% from cotton is conducted. However, an afforestation project that involved planting young trees led to an approximate 25% increase in water consumption. Overall, since 2012, the water-saving project has achieved satisfactory performance regarding excessive groundwater withdrawal, showing a reduction trend of 3 million m3/year and an increase in Lake Aiding water levels since 2011. The results reveal the potential of the ET monitoring strategy as a basis for basin-scale water management.

Highlights

There are longstanding concerns that freshwater resources are insufficient to satisfy the increasing demand from various segments of human society
Annual water consumption from bare soil and desert is typically less than 20 mm due to sparse precipitation, which is insufficient for growing plants
The 250-m resolution ET maps display reliable spatial patterns and temporal trends; water consumption is concentrated around the oasis with irrigation rather than with bare soil, and ET increased from 2006 to 2011 and decreased after 2012

Summary

Introduction

There are longstanding concerns that freshwater resources are insufficient to satisfy the increasing demand from various segments of human society. Water allocation is slanted towards industry and domestic use primarily due to their economic benefits. The spatial inhomogeneity of water resources is primarily affected by climate, which is difficult to change with human action. In addition to guiding water into appropriate areas, advanced irrigation technology (e.g., sprinkler and drip) can be applied to improve water use efficiency (WUE) by reducing non-beneficial soil consumption [9,10]. Inadequate allocation and irrigation programmes provide no water-saving guarantees because they typically fail to consider the hydrological cycle as a whole system [11]. The relationship between water consumption dynamics in water-saving measures should be considered. In reality, both systematic designation and stepwise policy optimization through monitoring are required

Objectives

Methods

Results

Conclusion