Water Chemistry Field Sampling
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of bedrock, soil type, geographic distribution of surface waters, presumed
sensitivity to stressors of interest, elevation, watershed area, lake area or
stream order, site accessibility, and avoidance of watersheds with other elements of human disturbance that might influence surface water composition. Approximate sampling site locations can be identified on a preliminary
basis from examination of available mapped data prior to initial sampling
trips, with specific site selection and further documentation developed in
association with sampling.
2.2.1.1.1 Features of Landscape Associated with Acid
Sensitivity of Surface Waters
It is not possible to define a priori the features of the landscape that will be
most closely associated with surface water acid nutrient or toxin sensitivity
nationwide. Such relationships are highly variable across the landscape and
should be expected to vary from region to region, sometimes from site to site.
Nevertheless, for a given region or study area, it is often possible to identify
certain landscape features that correlate with sensitivity or effects. Most commonly, these include such features as lithology, elevation, watershed area, and
watershed slope. Sometimes vegetation type (e.g., coniferous forest, alpine and
subalpine vegetation), soil type, or one or more regional soil variables (e.g., pH,
depth, percentage clay fraction) may also be helpful. Ecoregion designations
incorporate many of these variables and can also be useful. In general, the most
acid- and nutrient-sensitive lakes and streams are expected to occur under the
following conditions:
• bedrock that is not basaltic and does not contain appreciable amounts
of carbonate
• relatively high elevation
• steep terrain
• small watershed
• thin soils
• low soil clay content and low soil pH
• flashy hydrology
In the southeastern United States, south of the line of the most recent glaciation, acid-sensitive streams are often associated with siliciclastic bedrock
lithology (cf., Sullivan et al. 2007). In glaciated regions, the presence of varying
amounts of glacial till can obfuscate relationships between lithology and surface water chemistry. Sensitive lakes and streams often, but not always, occur
at relatively high elevation, on steep slopes, in relatively small watersheds.
Knowledge of such relationships, especially if that knowledge is regionally specific, can aid in selection of surface waters for inclusion in inventory and monitoring programs.
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of bedrock, soil type, geographic distribution of surface waters, presumed
sensitivity to stressors of interest, elevation, watershed area, lake area or
stream order, site accessibility, and avoidance of watersheds with other elements of human disturbance that might influence surface water composition. Approximate sampling site locations can be identified on a preliminary
basis from examination of available mapped data prior to initial sampling
trips, with specific site selection and further documentation developed in
association with sampling.
2.2.1.1.1 Features of Landscape Associated with Acid
Sensitivity of Surface Waters
It is not possible to define a priori the features of the landscape that will be
most closely associated with surface water acid nutrient or toxin sensitivity
nationwide. Such relationships are highly variable across the landscape and
should be expected to vary from region to region, sometimes from site to site.
Nevertheless, for a given region or study area, it is often possible to identify
certain landscape features that correlate with sensitivity or effects. Most commonly, these include such features as lithology, elevation, watershed area, and
watershed slope. Sometimes vegetation type (e.g., coniferous forest, alpine and
subalpine vegetation), soil type, or one or more regional soil variables (e.g., pH,
depth, percentage clay fraction) may also be helpful. Ecoregion designations
incorporate many of these variables and can also be useful. In general, the most
acid- and nutrient-sensitive lakes and streams are expected to occur under the
following conditions:
• bedrock that is not basaltic and does not contain appreciable amounts
of carbonate
• relatively high elevation
• steep terrain
• small watershed
• thin soils
• low soil clay content and low soil pH
• flashy hydrology
In the southeastern United States, south of the line of the most recent glaciation, acid-sensitive streams are often associated with siliciclastic bedrock
lithology (cf., Sullivan et al. 2007). In glaciated regions, the presence of varying
amounts of glacial till can obfuscate relationships between lithology and surface water chemistry. Sensitive lakes and streams often, but not always, occur
at relatively high elevation, on steep slopes, in relatively small watersheds.
Knowledge of such relationships, especially if that knowledge is regionally specific, can aid in selection of surface waters for inclusion in inventory and monitoring programs.