STREAM CHEMISTRY IN THE SOUTHERN BLUE RIDGE: FEASIBILITY OF A REGIONAL SYNOPTIC SAMPLING APPROACH¹

Abstract

A pilot study, which was conducted in the Southern Blue Ridge geographical province of the Southeastern U.S., demonstrated the feasibility of a probability‐based regional synoptic design for the National Stream Survey, which is a project aimed at estimating the number and percentage of streams in various regions of the U.S. that are acidic or at risk from acid deposition. Estimated population distributions for key chemical variables were not appreciably affected by week‐to‐week variability in stream chemistry during the spring index period chosen for the study. Differences were observed in estimated acid neutralizing capacity (ANC), nitrate, and pH frequency distributions between spring and summer. Observations made at the downstream node did not represent the chemistry of the entire reach for some variables (ANC and nitrate) as indicated by differences in chemical concentrations between upstream and downstream sampling locations. Coefficients of variation in chemical species were low enough to provide a reasonably stable classification of streams based on ANC. Although median ANC, sulfate, and nitrate concentrations were quite low in the region, the probability of finding streams with ph < 6.3 is less than 1.3 percent at the α= 0.05 confidence level.

Acid-base chemistry of high-elevation streams in the great smoky mountains

“…Elwood, unpub, data;Messer et al, 1986;1988). Messer et al (1986Messer et al ( , 1988 did not observe any acidic stream reaches in their sampling of second-to fifthorder streams in the Southern Blue Ridge. The low ANC values at the study sites may be attributed to a combination of the presence of SO42-derived from atmospheric deposition and a bedrock source, a small capacity of the thin soils to retain SO42-, and a large export of NO3-.…”

A DECISION SUPPORT SYSTEM FOR WATER QUALITY DATA AUGMENTATION: A CASE STUDY1

“…Although the current EMAP-SWS site selection protocol is unpublished, the probability-based site selection protocol of the National Stream Survey (NSS), a prototype of EMAP , was recommended for use in other national environmental monitoring programs by Messer et al (1988). This approach uses a finite population of stream reaches from which to select the sample, while EMAP-SWS is currently sampling the streams as a continuous resource with an infinite population.…”

“…This approach uses a finite population of stream reaches from which to select the sample, while EMAP-SWS is currently sampling the streams as a continuous resource with an infinite population. The NSS, using a square sampling grid over topographic maps, located monitoring stations by following the downslope vector from each sampling point, continuing perpendicular to the elevation contours until a stream reach was intersected or the flow vector left the study region (Messer et al 1988). The DSS modified this protocol by laying the EMAP 27.1-km triangular sampling grid over an ortho-rectified surface.…”

APPLICATION OF A MULTIPURPOSE UNEQUAL PROBABILITY STREAM SURVEY IN THE MID‐ATLANTIC COASTAL PLAIN1

“…In simple random selection, these probabilities are equal for all potential sites (Cochran, 1977). Because of the practical problems inherent in defining all potential sampling sites within a continuous resource, sites for environmental sampling are often selected from a randomly located uniform grid over the study area (Messer et al, 1988;Scott, 1990;Stevens, 1997;Olsen et al, 1998). For environmental assessments, much of the expected variability in the observed conditions may often be attributable to one or more geographic variables, such as land use, geology, or soil conditions (Hem, 1985;Krebs, 1994;Drever, 1997).…”

“…Stratified random sampling was used for ground water quality assessments in the Potomac River Basin (Gilliom et al, 1995;Gerhart and Brakebill, 1996). A stream survey in the Southern Blue Ridge Mountains was designed by selecting streams in watersheds intersected by a randomly located systematic grid of points (Messer et al, 1988). A similar approach was used to design a stream survey in the Mid-Atlantic and Southeastern United States (Kaufmann et al, 1991).…”