**Assessment of the Impact of Land-Use Types on the Change of Water Quality in Wenyu River Watershed (Beijing, China)**

Yuanzhi Zhang1,2 and Yufei Wang1

*1Yuen Yuen Research Centre for Satellite Remote Sensing, Institute of Space and Earth Information Science, The Chinese University of Hong Kong (CUHK), Shatin, Hong Kong 2Laboratory of Coastal Zone Studies, Shenzhen Research Institute of CUHK, Shenzhen, China* 

#### **1. Introduction**

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Land use-land cover (LULC) change is one of the major environmental changes occurring around the globe. Water quality is one of such factors affected by LULC change, since it is a key component of a healthy watershed where it integrates important geomorphic, hydrologic, and some of the biological processes of a watershed (Hem, 1985). Alteration of any one of these processes will affect one or more water quality parameters (Peterjohn and Correll, 1984). Hydrologists and aquatic ecologists have long known that the surface across which water travels to a stream or a lake has a major effect on water quality. Accordingly, the relative amounts of particular types of land use-land cover (LULC) in a watershed will affect water quality as well (Griffith, 2002). Therefore, the change in land-use and management practices will give rise to the considerable impact on water quality.

The importance of the interrelationships between LULC and water quality is reflected by the increased recognition over the past two decades that non-point source (NPS) pollution has come into being the major environmental concern (Loague *et al,* 1998; Sharpley and Meyer, 1994; Griffith, 2002). Pollutants affecting water quality may come from point or nonpoint sources. Point pollution can be easily monitored by measuring discharge and chemical concentrations periodically at a single place. In the past several decades, the major efforts and funding of water pollution control programs focused on the point sources management, and the magnitude of the point source pollution problem has been reduced in many cases. However, NPS pollution presents great challenges because of their dispersed origins and the fact that they vary with the season and the weather, in addition to the fact that non-point inputs are often overlooked by human beings. Land cover influences water quality because land cover determines the type and quantity of NPS pollutants that may enter the water body.

There are a lot of studies examining non-point source pollution focused on the effects from runoff over the agricultural land and concluded that agricultural coverage strongly

Assessment of the Impact of Land-Use Types

Fig. 1. Map of Wenyu River Watershed in Beijing (China).

**3. Methodology** 

**3.1 Water quality monitoring** 

Watershed, but the studies linking land use to water quality are limited.

on the Change of Water Quality in Wenyu River Watershed (Beijing, China) 277

As the main drainage canal in the Beijing City, the problems of water pollution and water ecosystems degradation in Wenyu River watershed have come along with the economic development in these years. Several documents estimated the pollution status (Wang and Song, 2008; Shi, 2008; You *et al.,* 2009; Hua *et al.*, 2010) of Wenyu River and pointed out that the water environment of this area was under sub-health; additionally, some other authors put forward the reasonable strategies to restore the ecological environment and improve the water quality in Wenyu River Watershed (Zheng *et al.,* 2007; Wang *et al.,* 2008; You *et al.,* 2009). Although there have many studies noted the water quality problems in Wenyu River

An integrated approach (involving remote sensing, geographic information systems, statistical and spatial analysis, and hydrologic modeling) is used to link the relationship of land use-land cover and water quality in a regional scale. The soft-wares used in this study include ENVI version 4.3, ArcGIS version 9.3, and SPSS version 14.0 for Windows. Figure 2 shows the flowchart of examining the relationship between land-use and water quality.

Water samples were collected from twenty-four stations within Wenyu River watershed (see Figure 3) from May to August (on May 22, June 9, July 18 and August 18, respectively) in 2009, and each water sample collection was conducted after the rainfall. Most of these

stations distribute in the mid-upper stream area of the Wenyu River watershed.

influenced water nitrogen (Johnson *et al.*, 1997; Fisher *et al.*, 2000; Ahearn *et al.,* 2005), phosphorus (Hill, 1981), total suspended solids (Ahearn *et al.,* 2005) and sediments (Allan *et al.*, 1997). A number of documents have illustrated the increasing urban areas were another significant contributor to the water quality deterioration, since the impervious surface coverage can alter the hydrology and geomorphology of urban streams and give the negative impacts on urban stream ecosystems (Schueler, 1995; Paul and Meyer, 2001; Morse *et al.*, 2003), and runoff from urbanized surfaces carries greater sources of pollutants, which results in the increasing loading of nutrients (Emmerth and Bayne, 1996; Rose, 2002), heavy metals (Norman, 1991; Callender and Rice, 2000), sediment loadings (Wahl *et al.*, 1997) and other contaminants to the near stream waters.

In recent years, since 1978 when China has initiated her economic reform and open-door policy, rapid urbanization and economic expansion has resulted in massive land alteration. However, people only focus on the economic growth, and always neglect this factor that economy grows at the expense of the environmental destruction. In this study, therefore, we applied Landsat TM data (2000-2008) to examine the changes of land-use and establish the relationship between land-use types and water quality variables, and give the technical support which can help propose the appropriate strategy that will permit the sustainable regional development and protection of the ecological environment, and understand how it important to assess their potential impacts of landuse types on water quality changes in the watershed scale. This study also demonstrates an example of the issue of how LULC change is linked to water quality, one of the most precious resources on earth.
