30 X. Wang downstream from a point pollution source, which could be a WWTP, an IFD or a TRI site. All other monitoring sites were included in the second group, which represents the low human impact areas. Statistical analysis Several statistical analyses were used to analyze the spatial distribution patterns of habitat, land uses, and water quality measured with water chemistry, Fish (IBI), and Macroinvertebrate (ICI) indicators, in the study area. First, measures from the sites that were immediate upstream from WWTPs were compared with measures from sites that were immediate downstream from the same WWTPs with a paired t-test method to test the hypothesis that water quality decreased below WWTP discharge points. Further, an independent two-sample t-test was performed to test the hypothesis that water qualities of river segments in high human impact areas were worse than that of river segments in low human impact areas. Finally, biological, habitat, and water chemistry monitoring values from the river segments and land use distribution within corresponding catchment were analyzed using the Pearson’s correlation to reveal any possible relationships between biological indicators and land uses and riparian habitat indicator. Multiple regression was then used to determine the principle driving forces for biotic integrity within the LMR (Dyer et al., 1998a). The purpose of the analysis is to evaluate the strength of the impact of land uses on the quality of receiving waters. Several water-chemistry parameters that had very small sample sets or were dominated by detection limit were dropped from the analysis. Results and discussion The results of this study are presented and discussed from three aspects—the impact of wastewater treatment plants, the spatial patterns of river-water quality, and the relationship between land uses in catchments and water quality of the receiving water. The importance of considering water quality in land-use planning is discussed based upon the findings from this study. Impact of wastewater treatment plants Table 2 displays the results from a paired t-test of the IBI, ICI, and QHEI in reference to WWTP discharge points. The IBI measurement from the closest sites to the discharge points demonstrated a statistically significant decrease of water quality downstream from WWTP discharges. Although both ICI and QHEI demonstrated similar trend, the change was not statistically significant. This implies that the water quality may not change significantly below and above WWTP discharge points. The lack of strong impact may be attributed to the better municipal WWTP practices (OEPA, 1995). The result concurs with findings by others that improved management of sewage reduced the impact on receiving waters (Wichert, 1995; Frenzel, 1990). The result also suggests a further study to analyze the discrepancy of the sensitivities of fish indicators (IBI) and invertebrate indicators (ICI) to WWTP discharges. Spatial patterns of water quality A visual examination of spatial distributions of the urban land use shows that there are two major urban areas within the LMR watershed. One is near the basin outlet at the lower left portion of the watershed and another is at upper left. In addition, there are a few smaller settlements scattering within the watershed (Figure 3). It is noticed that various types of point pollution sources are also concentrated in or near the more urbanized areas. A t-test of the Table 2. Matched-pair t-test of water quality from upstream and downstream of WWTPs Variable Paired differences a t df Significance (1-tailed) Mean SD IBI 4Ð769 9Ð471 1Ð816 12 0Ð0472 Ł ICI 1Ð000 7Ð886 0Ð439 11 0Ð3345 QHEI 1Ð875 20Ð190 0Ð256 11 0Ð3770 a Paired difference is calculated as downstream monitoring value minus upstream monitoring value for the same WWTP.
Water-quality and land-use planning 31 N * * * * * * * * * * * * * * * * * * * ** * * ** * * ** * * * * * * * * * * * * * ** * * * ** ** * * * * * * ** * * * * * * * * * * * * * * * * ** * ** * 10 0 10 kilometers Figure 3. Urban land and point pollution sources. Industrial facility discharge sites (Ł); wastewatertreatment plants ( ); toxic release inventory sites ( ); Little Miami River (. . .); watershed boundary ( ). mean monitoring values from the sites in the high and low human impact areas was performed upon the three indicators (Table 3). Both IBI and ICI values demonstrated significantly lower values in high human impact areas. It was interesting to note that habitats also showed lower quality in those areas, as indicated by low QHEI scores. These results imply that the biological integrity in rivers flowing through high human impact areas tend to be lower. Land uses and water quality of the receiving waters Among the 22 catchments, urban land percentages varied from 1% to 58% and