HR: 1340h
AN: H23D-1457    [Abstracts]
TI: Changes in Stream Water Quality Related to Land Use and Watershed Scale in the Catskill Mountains of New York State
AU: * McHale, M
EM: mmchale@usgs.gov
AF: U.S. Geological Survey, 425 Jordan Road, Troy, NY 12180 United States
AB: New York City`s West-of-Hudson reservoir system supplies about 85% of the city`s water supply. Land use management in this region has strong implications for water quality because it is the water supply for 9 million people. The city needs information on the effects of current and future land use on water quality. To address these needs the U.S. Geological Survey operates 34 stream gaging stations within the West-of-Hudson reservoir system in the Catskill Mountains of New York State. Water quality and stream flow data are collected at 12 of these sites, grab samples are collected bi-weekly and storm samples are collected using automated samplers. The gages are arranged in a nested watershed design with one or more forested ``upper-nodes`` and a ``lower node`` located at some distance downstream. The watersheds range in size from 2.0 to 177.7 km² and data for this study were collected from 2000 to 2004. The two principal land uses within the region are forest and agriculture. Residential and commercial land use account for less than 1% of the area in the watersheds included in the study. Watersheds with agricultural land use greater than 2% had the highest median concentration of total phosphorus (TP) and total dissolved phosphorus (TDP) in stream water, but there was no relation between the percentage of agricultural land use and TP or TDP concentration. The watershed with the highest percentage of agricultural land use (38%) had TP and TDP concentrations similar to another watershed with 3% agricultural land use. The highest TP and TDP stream water concentrations were measured in a watershed that had 20% agricultural land use, but was the smallest of the lower node watersheds (37 km²). Likewise there was no relation between land use and median nitrate concentration, indeed the highest median nitrate concentration was measured in a watershed that was 99% forested. Water quality from forested watersheds had lower nutrient concentrations than that from agricultural watersheds, although not all agricultural watersheds had high nutrient concentrations. Since agriculture in this region typically consists of small, family-operated dairy farms, their influence on water quality is small. Base cations increased from upper nodes to lower nodes as did pH and acid neutralizing capacity, but these increases were not related to land use. Neither changes in flow nor change in basin size was correlated with the change in water chemistry from upper nodes to lower nodes. These results underscore the difficulty in trying to generalize the effect of land use on stream water quality in areas where there are not large variations in land use or when land use does not profoundly affect the landscape. Analysis of individual storms that occurred in all of the watersheds may provide additional insight into watershed responses during high flow.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1806 Chemistry of fresh water
DE: 1839 Hydrologic scaling
DE: 1860 Streamflow
DE: 1880 Water management (6334)
SC: Hydrology [H]
MN: Fall Meeting 2005