NUTRIENT CONCENTRATIONS AND YIELDS IN UNDEVELOPED STREAM BASINS OF THE UNITED STATES¹

Abstract

Data from 85 sites across the United States were used to estimate concentrations and yields of selected nutrients in streams draining relatively undeveloped basins. Flowweighted concentrations during 1990-95 were generally low with median basin concentrations of 0.020, 0.087, 0.26, 0.010, and 0.022 milligrams per liter (mg/L) for ammonia as N, nitrate as N, total nitrogen, orthophosphate as P, and total phosphorus, respectively. The flow-weighted concentration of nitrate exceeded 0.6 mg/L in only three basins. Total nitrogen exceeded 1 mg/L in only four basins, and total phosphorus exceeded 0.1 mg/L in only four basins. The median annual basin yield of ammonia as N, nitrate as N, total nitrogen, orthophosphate as P, and total phosphorus was 8

Loading of phosphorus and nitrogen to Lake Waco, Texas

“…The estimated annual export of P is 0.15 kg/ha/yr, while for N it is 1.4 kg/ha/yr. These values are consistent with expectations from the literature (Reckhow et al 1980, Clark et al 2000. Subtracting this background load from total loads for subwatersheds with dairy farms and/or WAF but no WWTF provides an indication of dairy operation inputs (Table 10).…”

“…The TP and TN levels are very high in the streams in this area, and the TN:TP ratio is low, indicative of inputs of animal wastes. Export coefficients for water are generally low and typical of this geographic area (Central Texas;Dunn and Leopold 1978), while export coefficients for TP and TN are quite high in most cases (Clark et al 2000). …”

Sampling Considerations for Establishment of Baseline Loadings from Forested Watersheds for TMDL Application

“…~e l a t i v e l~ high NO3 concentrations during both the growing and dormant season are theorized to result from nitrogen saturation, compared to more varying concentrations within-storms and among-seasons in ecosystems where nitrogen is still limiting (Stoddard, 1994). But even with the greater variability in NO3 concentrations that might be expected in the absence of nitrogen saturation, low-intensity sampling probably would be applicable in other forested watersheds because the range of reported NO3 (and total nitrogen) concentrations is fairly small from both undisturbed forested watersheds (Clark et al, 2000;Martin et al, 1986) and man-.…”

Natural Background Concentrations of Nutrients in Streams and Rivers of the Conterminous United States

“…(ii) Nutrient yields at undeveloped reference sites vary by more than 2 orders of magnitude (8,10,11) because of variations in any of several basin characteristics including climate, hydrology, natural vegetation (8), and the mineral composition of soil and rock (12). Thus, estimates of background conditions for developed regions should reflect the natural characteristics of the specific watersheds of interest.…”