Agriculture Reference
In-Depth Information
high [4]. Thus, understanding the effects of intensive agricultural land use
activities on water resources is essential for natural resource management
and environmental improvement. However, these effects on water quality
conditions are difficult to determine because of the complex relationships
between agricultural land use activities and water quality.
In previous studies water quality was generally linked to land use in-
side the catchments area. Several studies have found that land use has a
strong infl uence on the receiving water body quality [5-7]. The majority
of studies about the effects of land use on water quality have focused on
either deterministic modeling, or spatial, or statistical analyses. Examples
of modeling studies include those performed by Tong and Chen [5], Chap-
lot et al. [8], Cao et al. [9], Bhattarai et al. [10], etc. which have adopted
the existing watershed-scale hydrological variables and nonpoint-source
pollution models to evaluate or predict how land use/land cover scenarios
affect water quality. Since modeling methods need long-term water qual-
ity monitoring data and regional parameters are diffi cult to obtain, cur-
rent modeling methods are still developmental and confi ned to mechanism
studies in local watersheds. Consequently, there are more studies that have
adopted statistical methods such as correlation analysis [11,12], single lin-
ear regression analysis [13,14], multiple linear regression analysis [15-
17], nonparametric statistical analysis techniques [18], etc. to examine the
relationships between watershed land use/land cover and water quality.
Since no statistical signifi cant relationships between land uses and ni-
trate level were found when using the whole basins, contributing areas
inside buffer zones were developed by Basnyat et al [19]. There have been
more subsequent studies taking buffer zones as analysis units to explore
water quality characteristics and their relationships [20-22]. The defi ni-
tion of contributing zone may open additional ways of visualizing the
problem. The previous studies have demonstrated that the contributing
zone is infl uenced by many factors, including the water-quality parameter
being assessed and geomorphic/climatic setting of the watershed [19]. To
some extent, buffer zones with multi-scale characteristics, created using
the distance from the stream, are not true hydrological units, and they are
diffi cult to delineate and explain the hydrological and ecological condition
of the stream validly. To overcome this, our study defi nes the multi-scale
nested watersheds based on the basic watershed units created by a digital
 
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