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The proportion of cropland cover in the catchments of Missouri reservoirs, a surrogate for non-point-source nutrient loss from agricultural watersheds, accounts for some 60%70% of the cross-system variance in long-term averages of total phosphorus and total nitrogen (n=126, ln transformation for nutrients and logit for cropland). The addition of dam height and an index of flushing rate improved r2 values to ~77% for both nutrients. Even among reservoir catchments with >80% grass and forest cover, cropland accounted for most of the variation in nutrients. Reservoir nutrients showed a strong negative relation to forest cover. Relations between grass cover and nutrients were positive but weak, and grass had no significant...
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Data from 129 shallow riverine takes within the Yukon Flats National Wildlife Refuge (between 65degrees 45degreesN and 67degrees 30degreesN and 142degrees 30degreesW and 150degrees 00'W) are presented as a baseline contribution to the regional limnology of Alaska. Ion composition reflected the composition of carbonate alluvium within the region; in most lakes Ca > Mg and bicarbonate dominated the anions (similar to90%). In lakes where alkali deposits occurred, Na, Mg and bicarbonate were the principal ions. Some 25% of the takes were slightly brackish (conductivity >500 S) to brackish. The lakes are colored, with 18 to 447 Pt-units. And, they are fertile, with over 70% classified as eu-or hypereutrophic on the basis...
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