Impacts of Land Use on Surface Water Quality in a Subtropical River Basin: A Case Study of the Dongjiang River Basin, Southeastern China

Abstract

Abstract:Understanding the relationship between land use and surface water quality is necessary for effective water management. We estimated the impacts of catchment-wide land use on water quality during the dry and rainy seasons in the Dongjiang River basin, using remote sensing, geographic information systems and multivariate statistical techniques. The results showed that the 83 sites can be divided into three groups representing different land use types: forest, agriculture and urban. Water quality parameters exhibited significant variations between the urban-dominated and forest-dominated sites. The proportion of forested land was positively associated with dissolved oxygen concentration but negatively associated with water temperature, electrical conductivity, permanganate index, total phosphorus, total nitrogen, ammonia nitrogen, nitrate nitrogen and chlorophyll-a. The proportion of urban land was strongly positively associated with total nitrogen and ammonia nitrogen concentrations. Forested and urban land use had stronger impacts on water quality in the dry season than in the rainy OPEN ACCESSWater 2015, 7 4428 season. However, agricultural land use did not have a significant impact on water quality. Our study indicates that urban land use was the key factor affecting water quality change, and limiting point-source waste discharge in urban areas during the dry season would be critical for improving water quality in the study area.

How Do Terrestrial Determinants Impact the Response of Water Quality to Climate Drivers?—An Elasticity Perspective on the Water–Land–Climate Nexus

“…Sub-class dense settlements ratio was higher in the Mekong watershed with annual rainfall (median) of 1051 mm [36]. Precipitation exacerbated the deterioration of surface waters due to high overland flow in dense settlements [63].…”

“…Few studies have shown that forest land cover has a positive relation with nitrogenous materials [47,74,75]. It could be attributed to higher water discharge and lower water residence time, which affects the uptake capacity of vegetation [63]. Populated forests with human intrusion (mean population density of 3 persons/km 2 ) and a higher annual rainfall of 1090 mm, were in higher ratio at the Mekong watershed compared to remote forests.…”

“…Table 2 displays that ε P (P, NO X -F) and ε P (P, P-F) were sensitive and positively correlated to dense settlement biomes. Dense settlement had intensifying effects on increasing nitrogen loads, phosphorus and other nutrients in surface water [16,[55][56][57][58][59][60][61][62] due to high anthropogenic activities and low retention capacity in urban lands [63]. There might be a high nitrogen emission when people practice urban gardening or do not have sewage plants etc.…”

Impacts of Environmental Variables on a Phytoplankton Community: A Case Study of the Tributaries of a Subtropical River, Southern China

“…In addition, all the nutrient parameters in this river were much higher than those of the others. This was closely connected with the high intensity of human activities [24]. Large amounts of incompletely treated sewage (e.g., municipal wastewater and industrial effluent) are discharged into the rivers, which is a problem in tropical Asian watersheds with dense populations and industries [39].…”

“…Although there are several large reservoirs in the basin, the hydrology and water availability of the basin still demonstrate strong seasonal variations [23]. The Li River, Qiuxiang River and Danshui River are three tributaries of the Dongjiang River and are respectively located upstream, midstream and downstream of the Dongjiang River [24]. The Li River originates from Liyuan Town and is approximately 100 km long.…”