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Influences of spatial scale and soil permeability on relationships between land cover and baseflow stream nutrient concentrations
Citation:
DANIEL, F. B., M. B. GRIFFITH, AND M. E. TROYER. Influences of spatial scale and soil permeability on relationships between land cover and baseflow stream nutrient concentrations. ENVIRONMENTAL MANAGEMENT. Springer-Verlag, New York, NY, 45(2):336-350, (2010).
Impact/Purpose:
The purpose of this research project is to provide methods, tools and guidance to Regions, States and Tribes to support the TMDL program. This research will investigate new measurement methods and models to link stressors to biological responses and will use existing data and knowledge to develop strategies to determine the causes of biological impairment in rivers and streams. Research will be performed across multiple spatial scales, site, subwatershed, watershed, basin, ecoregion and regional/state.
Description:
The Little Miami River (LMR) basin, dominated by agriculture, contains two geologically-distinct regions; a glaciated northern till plain with soils three times more permeable than a southern, pre-Wisconsinan drift plain. The influences of two landscape measures, percent row crop cover (%RCC, computed at three spatial scales), and soil permeability (PERM) on baseflow nutrient concentrations were modeled using linear regressions. Quarterly water samples collected for four years were analyzed for nitrate-N (NN), Kjeldahl-N (KN), total-N (TN), and total-P (TP). In till plain streams (n-17), NN concentrations were 8.5 times greather than drift plain streams (n-18), but KN and TP were 20-40% lower at comparable %RCC. These differences resulted in TN /TP molar ratios >80 in till plain streams, but <6 in drift plain streams. For till plain streams regression models based on %RCC accounted for 79% of the variance in NN concentrations but only 27% in drift plain streams. However, regressions on %RCC accounted for 68-75% of the KN and TP concentration variance in the drift plain streams but essentially none in the till plain. Catchment PERM influenced the regional NN/KN ratios which were 10-fold higher in the drift plain streams. For both till and drift streams the catchment scale %RCC gave the best predictions of NN, a water soluble anion, but the smaller spatial scales produced better models for insoluble nutrient species (e.g., KN and TP). A literature review for Ohio streams suggests that these inter-regional differences in nutrient ratios have potential implications for aquatic biota of receiving streams.