Evaluation of livestock pollution and its effects on a water source protection area in China

Livestock and poultry (LP) pollution affects water quality of water resources. In this study, spatio-temporal variations in amount, structure, and discharge of LP pollutant in the water source area of the Middle Route of South-to-North Water Diversion Project (MR-SNWDP) in China on the county scale were analyzed. In this regard, the gray water footprint (GWF) was employed as an indicator for quantitative evaluation of LP pollution to measure the impact of these parameters on local water resources. Based on the statistical data for the time period of 2000-2017, the results showed that the total amount of LP farming has steadily increased, except for a slight decrease in the years 2007 and 2014. Also, the counties, Dengzhou (DZ), Neixiang (NX), and Xichuan (XC), are found to be the biggest polluters. The GWF of total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) was calculated to be 12.7, 8.6, and 2.8 billion m³ in 2017, respectively, with GWF_TN > GWF_TP > GWF_COD. The pollution of TN caused by LP has a greater impact on water quality than COD and TP. In 2017, the water pollution level (WPL) of water source area is 0.28, it means LP pollution required 28% of the total local water resources to be diluted. Additionally, the WPL for DZ, NX, and XC was found to be greater than 1, and it is concluded that the water resources of these regions face an environmental threat. Based on the area scale of the water sources, policies and incidence of diseases mainly affected the changes in the number of LP farming. On the county scale, the total amount and structure of LP was affected by factors such as terrain, traffic, economic level, and breeding mode. It is recommended that different policies and disposal methods should be adopted based the LP farming conditions in different cities.