The Influence Of Land Use On Water Quality In Suzi River Watershed In The Upper Dahuofang Reservoir

With the support of ERDAS, ArcGIS and GPS software, the land-use type and thedistribution of the landscape patterns were analyzed by using the ALOS image in2010in thewatershed of Suzi River. Based on the data of historical water quality, the correlation andredundancy analysis（RDA）methods were used to analyze the relationship between waterquality and land use patterns within the different scale of buffer zones. Based on the landscapemetrics in different scale of buffer zones, the influence of landscape pattern on the waterquality was analyzed.The results were as follows:（1） The landscape patches of Suzi River watershed tended to be fragmentation, thelandscape heterogeneity is lower at the landscape level. Forest is the main advantaged oflandscape types which area ratio of forest is more than70%of the overall, the distribution offorest patches is relatively concentrated; the connectivity among the forest patches is high.Dry land is the second largest landscape type in Suzi River watershed, the patches number ofwhich is higher, and the patches connectivity of which is relatively low. The landscapefragmentation degree of paddy and buildings are more severe, the patches shapes of these twotypes have a tendency to tend to be irregular. The areas of grassland, unused land and miningland are small and have a little change, and their patches’ distribution is scattering.（2） In the6kinds of different scale, the area proportion of the8types have differentchange rule. Within50meters,100meters,200meters buffer zones, paddy, dry land, forest,building, grassland and unused land played a dominant role in explaining the change of waterquality, and have obviously effected on water quality. Paddy, dry land and building havepositive effect on TN、NH₄⁺-N、NO₃^--N and NO₂^--N. The area proportion of forest graduallyincreased with the increase of buffer distance, forest show negative effect on NH₄⁺-N、NO₃^--N.However, the effect of each land use types on the water quality reduced gradually along withthe increase of the buffer scale within300meters,400meters and500meters buffer zone.Paddy, dry land and building were the important factor on the deterioration of water quality.But the influence can be reduced due to increase of the buffer zone distance. The area ratio ofgrassland and unused land are below3%on the scale of watershed, the interpretation rate ofwater quality change rate can not to illustrate the impact of land use mode on water quality.Therefore, the range which has a buffer distance of less than200m is the most importantregion in the water quality in Suzi River.（3） Landscape pattern has different effect on the water quality of the river on differentwatershed scale: in the range which has a buffer zone less than300m, dry farming、buildingand paddy are the main landscape types. The landscape types have positive effect on the waterquality due to their higher patches density and count. Meanwhile, the largest patch index andthe largest shape of these types have sufficient positive correlation with the pollution indices of the river. The connectivity of dry farming patches is higher, so the dry farming has apositive effect on river water quality. Then the aggregation index of the landscape types hasnegatively correlated with the pollution indices of the water. In the far distance area, thedistance of the buffer zone more than300m, forest is the main patch landscape, theconcentration and connectivity of forest patches are relatively higher, the landscape pattern offorest has a positive effect on improving the water quality, but the phenomenon is not obvious.In a word, the landscapes pattern has an obvious effect on the water quality in the range whichbuffer zone distance is less than300m. This result shows that the landscape types which areinfluenced intensely by human activities such as farm land and building land have key effecton the water quality in Suzi river watershed. However, the distribution of the landscapespattern has no significant effect on water pollution index which the buffer zone distance ismore than300m.