Precipitation Effects on Sediment and Associated Nutrient Discharges from Rhode River Watersheds

Abstract

Total suspended sediment (TSS) concentrations and their nutrient composition were studied in discharges from seven contiguous small watersheds on the Atlantic Coastal Plain in Maryland for up to 22 yr. AU watersheds were equipped with V-notch weirs and volumeintegrating, Dow-proportional samplers. Spot samples were also taken for analysis of TSS concentrations and the composition of dissolved and particulate nutrients at known water discharge rates. Interannual variations in annual and seasonal precipitation during this study spanned approximately the range of 160-yr weather records in the vicinity. Mean annual TSS fluxes were 263,546, 134, and 92 kg ha-1 for the area-weighted mean of the overall Rhode River watershed, and for subwatersheds that were primarily-cropland, completely forested, and grazed, respectively. TSS fluxes were highest in the summer, foUowed by spring, winter, and faD. Regressions ofTSS Dux vs precipitation were used to calculate TSS fluxes for seasons and years with average, above and below the average precipitation. TSS Dux from the Rhode River watershed was 12-fold higher in very wet years than in very dry years and 271-fold higher in very wet summers than in very dry summers. At base Dow, TSS had high nutrient content, but as Dow rates increased TSS nutrient content rapidly declined. At base Dow, most of the totai-P, TPi, TKN, and organic-C was in the dissolved phase, while at higher flows, most of these nutrients were in the TSS phase.T HE DISCHARGE of total suspended sediment (TSS) from watersheds into receiving waters can become a serious problem when natural vegetation is replaced by agriculture or urbanization Reid and Frostick, 1994). TSS is, by weight, the most important aquatic pollutant and also contains large amounts of nutrients and other pollutants, some of which may later be released into the water column of the receiving waters. Many studies have measured the fluxes of TSS from small watersheds dominated by cropland (e.g., Alberts et al., 1978;Burwell et al., 1977; Schuman et al., 1973a,b ), pasture land (e.g., Doran et al., 1981;Owens et al., 1982Owens et al., , 1983a Owens et al., ,b, 1989 Schuman et al., 1973a,b;Smith, 1992), and forest (e.g., McDowell and Asbury, 1994;Naiman, 1982;Owens et al., 1983aOwens et al., , 1989. Other studies have measured TSS fluxes from larger mixed land use watersheds (e.g., Haith and Shoemaker, 1987;Jordan et al., 1986;Kronvang, 1992 Many studies also have examined the nitrogen and phosphorus content of the TSS discharged from study watersheds and compared this with the discharge of dissolved nutrients (e.g., Alberts et al., 1978; Cooke, 1988a,b;Duffy et al., 1978;McDowell and Asbury, 1994; Schuman et al., 1973a,b ). Some studies also measured the organic-C content of the TSS (e.g., Mulholland, 1981;Naiman, 1982;McDowell and Asbury, 1994). These studies concluded that most of the organic-P, TPi, and organic-N is discharged in the TSS. Many of these studies also developed regression models to describe the relationships among wat...

Effects of land use on benthic macroinvertebrate communities: Comparison of two mountain streams in Korea

“…In contrast, Odae Stream, which has a mostly undisturbed watershed, exhibited little variation in these factors over the seasons. These results are in agreement with other studies on the relationships of precipitation, SS, and nutrient contents of watersheds (Correll et al, 1999;Cre´taz and Barten, 2007). Well-preserved streamside vegetation, as in the Odae Stream watershed, can prevent soil erosion and nutrient release into adjoining streams because it stabilizes the stream banks.…”

Temporal variability of optical properties in a shallow, eutrophic estuary: Seasonal and interannual variability

“…Location of the automated samplers is given in Gallegos et al (1992). Flow was measured at V-notch weirs, and samples in volumes proportional to the flow were pumped into acid-washed glass carboys (Correll, 1981;Correll et al, 1999). Samples were composited weekly and analyzed for TSS concentration as described above.…”

“…The quantity and quality of underwater light drive photosynthesis by phytoplankton, benthic algae, and submersed macrophytes (Kirk, 1994). Light is required for feeding by visually orienting predators (Aksnes et al, 2004), and the visual appearance of a water body is a key factor in the aesthetic and recreational appeal to humans (Davies-Colley et al, 1993). Understanding the factors controlling the variability of optical properties in coastal waters is important, because changes in the optical properties of a water body can be both indicators of stressors such as eutrophication, and can be potential stressors to components of the ecosystem, e.g.…”

“…Estuaries are optically complex systems due to the sources, sinks, and transformations of terrestrially derived dissolved and particulate matter that mixes with coastal-derived water that is likewise optically complex (Davies-Colley et al, 1993). Flocculation of river-borne clay particles occurs with small increases in salt concentration, changing the effective size distribution and settling rate of suspended solids (Postma, 1967).…”

Nonpoint source pollution loading from an undistributed tropic forest area

“…There are many NPS studies from forest land in general and undistributed forest in particular. For example, studies have included the effect of forest operation on NPS pollution (Grace 2004(Grace , 2005, simulation of the dissolved inorganic nitrogen (DIN) from forest associated with gypsy moth defoliation (Wang et al 2003), effect of forest roads on erosion losses (Grace 2002), seasonal variations (Correll et al 1999), estimation of suspended sediment quantity (Fowler and Heady 1981), NPS survey from 20 Northeastern region (Edwards and Stuart 2002), evaluation of "buffered zones" to reduce nitrate migration (Basnyat et al 2000), erosion effect (Sidle et al 2006), specific loads of various pollutants (Umemoto et al 2001), nutrient use pattern (Lodhiyal and Lodhiyal 2003), and nitrogen export to streams (Li et al 2004). …”