『Abstract
Water pollution in response to accelerated land-use/land cover
changes has drawn concerns because of public health and environmental
impacts. The study was conducted to evaluate the impact of land
use/land cover changes, seasonal, and location on water quality
of streams within the Wheeler Lake Basin in northern Alabama.
Temporal water samples from 18 streams were randomly collected
in 2000 and 2001, processed and analyzed for pH, and total nitrogen
(TN), dissolved (Dp), particulate (Pp) and total phosphorus (Tp),
dissolved oxygen (DO) and soluble lead (Pb) concentration, employing
standard methods of analysis. The data were normalized and integrated
into a simple index (WQCIndex) to evaluate
stream water quality. Results showed that the urban proportion
of the total watershed basin had increased from 2.9 to 14.7％ with
an associated loss of agricultural (8.9％) and wetland (4.8％) covers
from 1992 to 2000. A change in land-use/land covers in association
with seasonal and location variation significantly affected stream
water quality. Total nitrogen concentration in stream water had
a peak during the summer at 34％ above the annual mean. While both
Pp and Tp concentrations peaking during the summer at 24％ above
the annual mean and about 25％ below the annual mean during spring,
the DO concentrations were 46％ above the annual mean during the
fall and 18 to 26％ below annual mean during summer. The WQCIndex had responded very seasonal and showed significant
identical trends, with 21％ degradation in water quality during
the summer above the annual mean and improvement during the spring
at 20％ above the annual mean. Upstream water had a significantly
greater Pp and Tp (21 to 28％) concentration than at down- and
middle streams water. Location and seasonal variations had significant
interactive effects on Pp, Tp and DO concentration of stream water.
Total amount of seasonal rainfall significantly accounted 99.6％
of the variations in WQCIndex. Increasing
seasonal mean relative humidity, air and soil temperature, evaporation
and solar radiation had positive relationship with the variations
in WQCIndex. Among the water quality parameters,
both Pp and Tp were correlated (r 2 = 0.998***)
to each other, and accounted for more than 80％ variability of
the WQCIndex. Highly significant positive
linear relationship between Pp and Tp concentration suggested
that 99.8％ of the P in stream water is in Pp form which probably
transported with sediments in surface runoff. In other words,
Pp is the main pollutant responsible for degradation of stream
water quality in the Wheeler Lake Basin. Routine measurement of
the either Pp or Tp concentration could be used as sensitive and
early indicator of temporal changes in stream water quality even
when the other parameters changed negligibly or remain unchanged.』
Introduction
Materials and methods
Description of study area
Sampling, processing and analysis of water samples
Statistical analysis
Results and discussion
Temporal changes in the land-use/land cover types in the
Wheeler Lake Basin
Effects of temporal land-use/land cover changes on stream water
quality
Relationship between water quality index and climatic parameters
Relationship between water quality index and water quality parameters
Conclusions
Acknowledgements
References