Application of Export Coefficient Model and QUAL2K for Water Environmental Management in a Rural Watershed

Zhuohang Xin,Chi Zhang,Lei Ye

doi:10.3390/su11216022

Abstract

Water quality deterioration caused by excessive nutrient discharge from various point and non-point sources are a global challenge. Understanding the pollution sources and their respective contribution is the prerequisite for environmental planning, management and restoration. In this study, the influence of complex pollution sources on the water quality of the Dengsha River watershed in Dalian, China, was investigated. The export coefficient method was coupled with the QUAL2K water quality model to estimate the loads of ammonia nitrogen (NH4-N) and total phosphorus (TP) from different sources, and to explore their respective contributions. Results indicated that animal feedlot and crop production were major sources for NH4-N load, and crop production, soil erosion and animal feedlot are the largest three sources of TP load with an annual total contribution of 98.4%. The pollutant load exhibited an intra-annual variation mainly due to the seasonality of rainfall and anthropogenic agricultural activities. The overall waste assimilation capacity (WAC) is overloaded and suggestions for water pollution control and treatment regarding each pollution source were proposed. This study addressed a new application of QUAL2K model coupled with the export coefficient model for watershed managers towards a sustainable water environmental management, and can therefore be a reference example for other small and medium-sized rural watersheds.

Highlights

Water environment issues associated with rapid economic development have become one of the most critical concerns facing both the national and local governments in many regions of the world [1,2]
The annual NH4-N load from the study region was 32.9 t, of which 71.7% was from the upper part, and 28.3% was from the lower part
The contributions to NH4-N ranked as animal feedlots (62.5%), crop production (17.6%), rural households (17.6%), industry (16.0%) and soil erosion (0.8%), respectively

Summary

Introduction

Water environment issues associated with rapid economic development have become one of the most critical concerns facing both the national and local governments in many regions of the world [1,2]. Under the requirement of rapid economic development, as well as the rising public desire for a better ecosystem, the Chinese government has implemented a series of comprehensive policies to safeguard the nation’s waters, such as the Action Plan for Water Pollution Prevention and the River Chief System issued by the State Council in 2015 and 2016, respectively [5]. These are not independent plans but amalgamations of other plans and policies with wide-ranging impact across sectors. The water quality model can be an effective tool for simulating the pollutant migration and transportation processes from various point and non-point sources [8,9,10]

Objectives

Methods

Results

Conclusion