Identification of regional water resource stress based on water quantity and quality: A case study in a rapid urbanization region of China

Highlights

• Water resource stress was identified based on water quantity and water quality.

• The water resource stress patterns could be divided into four categories.

• The core counties of Beijing had the highest WF per capita in the BTHR.

• The NPS export intensities of the BTHR were much greater than other regions in China.

Abstract

The stress assessment of water resources is very important for water resource management. How to identify the patterns of water resource stress is urgently important in rapid urbanization regions. Existing studies typically focused on one aspect of water resources and have lacked the completion of a comprehensive analysis. This study proposed a quantitative method of hotspot analysis based on water quantity and quality. Using the Beijing-Tianjin-Hebei region (so-called Jing-Jin-Ji) of China as a case study, the water resource stress was assessed based on the calculations of the water footprint per capita and non-point source pollution export intensities at the county scale. The results showed that (1) The water footprint per capita had great spatial variability in this region, ranging from 524.37 m³ to 897.32 m³ of the counties, and the water footprint per capita was decreased in the order of Beijing (861.71 m³)＞Tianjin (748.92 m³)＞Hebei (566.74 m³). (2) The non-point source total nitrogen and total phosphors export intensities in this region were much higher than those in other regions of China. (3) The stress patterns of water resources in the Beijing-Tianjin-Hebei region's counties could be divided into four categories. More than 60% of the counties had a low water footprint per capita-high non-point source pollution pattern. The low water footprint per capita-low non-point source pollution counties were mainly in Zhangjiakou and Chengde, as well as some mountainous counties in the west of Baoding and Xingtai. The core counties of Beijing, Tianjin, Shijiazhuang, Baoding, Handan, and Qinhuangdao, and the northern mountainous counties of Beijing were high water footprint per capita-low non-point source pollution counties. The high water footprint per capita-high non-point source pollution counties were primarily the non-core counties of Beijing and Tianjin. This study indicated that the priority counties in terms of water resource management could be identified by combining the water footprint with non-point source pollution exports. This method can be easily extended to other regions at home and abroad.

Introduction

Statistical data showed that the global water consumption in the last century increased almost six-fold (Margaux, 2012), and is predicted to rise by a further 50% in developing countries and 18% in developed countries by 2035 (WWAP, 2006). There are still more than 800 million people lacking a safe supply of freshwater and 500 million people are getting increasingly closer to risking this situation (Zeng et al., 2012, Miglietta et al., 2017). The emerging water crisis is becoming one of the most serious changes facing humans in the 21st century (Dong et al., 2013, Zhao et al., 2017). As the largest developing country in the world, China has been under the increasing pressure from water shortages in recent years due to rapid development and urbanization (Zhao et al., 2009). For example, as much as 609.5 billion m³ of freshwater resources were consumed in China in 2014, which accounted for 15% of the global water withdrawal (Zhao et al., 2017). However, the water resource amount per capita of China ranks 121^st in the world and is only approximately 25% of the world's average value (Ge et al., 2011). The Water footprint (WF) is a good consumption-based indicator of water use and was introduced by Hoekstra and Hung (2002). Since the WF concept was introduced in China, many scholars have successfully applied this novel method to evaluate the water demand and utilization status at the national (Zhao et al., 2009, Ge et al., 2011, Wang et al., 2016) and regional (Zhao et al., 2010, Zhang et al., 2012, Qian et al., 2018) scales.

Non-point source (NPS) pollution is a severe threat to aquatic environments and a major contributor to eutrophication and other problems as regards water pollution (Liu et al., 2009, Ongley et al., 2010, Collick et al., 2015). USEPA (1995) has reported that NPS pollution was the primary contributor to water pollution, and 60% of water pollutants were derived from NPS pollution in the USA. In China, the contribution of NPS pollutants to total water pollution was estimated to be as high as 81% for nitrogen (N) and 93% for phosphorus (P) (Ongley et al., 2010). People have paid increasing attention to NPS pollution in recent decades, and numerous studies have focused on estimating NPS pollution and proposing management measures (Hanrahan et al., 2001, Ma et al., 2011, Wang et al., 2015).

The Beijing-Tianjin-Hebei region (BTHR, so-called Jing-Jin-Ji) is located in northern China and had a recorded population of 1.196 × 10⁸ in 2014, which accounted for 8.74% of the total population of China. The BTHR has experienced rapid urbanization, and the total urbanization rate was 58.93% in 2012; specifically, the urbanization rates in Beijing, Tianjin, and Hebei were 86.2%, 81.55%, and 46.8%. However, the BTHR is also a region with severe resource shortages. The water resource per capita was 124 m³ in 2014, which accounted for only 6% of the average in China. The water resources per capita in Beijing, Tianjin, and Hebei were 94 m³, 74 m³, and 143 m³. With rapid economic development and urbanization, river water quality has seriously deteriorated, and water quality in most rivers in northern China is far below the standards related to national drinking water quality. Among the problems related to water pollution, eutrophication is particularly prominent. The BTHR is located in the main region of the Haihe River Basin, and Zhang et al. (2015) has reported that 44% of the main rivers in the Haihe River Basin were extremely eutrophic. Therefore, the BTHR is under stress in terms of both water quantity and water quality. Thus, the BTHR represents a typical region that can be used to study water resource stress by linking the WF with the NPS pollution. However, to our knowledge, few studies have focused on water resource problems from the perspectives of both water quantity and water quality in such a typical region.

In this study, a bottom-up method was used to estimate the WF per capita (WF_pc) from domestic water, crop and animal products, and an improved export coefficient model was used to stimulate the NPS pollution export intensities from the rural population, livestock husbandry, and land use across 201 counties in the BTHR. The objectives of this paper were to (1) estimate the WF_pc and the NPS TN and TP export intensities at the county scale in the BTHR and (2) identify the stress patterns of water resources according to the WF_pc and NPS exports.