Event Title

Stream Water Chemistry Differences in Watersheds of Varying Land Cover and Lake Abundance

Presenter Information

Phil Brown

Location

Space Dynamics Laboratory

Event Website

http://water.usu.edu/

Start Date

3-25-2004 11:55 AM

End Date

3-25-2004 12:00 PM

Description

Evidence is building that atmospheric deposition of anthropogenic inorganic nitrogen and phosphorous is increasing in high elevation watersheds throughout the western United States. Nitrogen released from the burning of fossil fuels and phosphorous released from agricultural lands enters the atmosphere and can be deposited in mountain watersheds via rain and snow. Nitrogen and phosphorous are key limiting nutrients, and therefore even minor increases could have a measurable effect on the oligotrophic lakes and streams within this region. The land cover characteristics of a watershed can have a significant impact on the amount of nitrogen and phosphorous that is released into streams and lakes. Watersheds with relatively low proportions of forest and high proportions of bare rock will leach more nitrogen and phosphorous into surface waters. Heavily forested watersheds will leach less of these nutrients, as they are assimilated by vegetative and microbial processes. Determining the relationship between land cover and stream chemistry within a watershed is useful for understanding the effect of nutrient additions and land use alterations on the ecology of inland waters. Ten watersheds and two subwatersheds within the Sawtooth Mountains of central Idaho were sampled in our study. Each watershed has varying proportions of forested (subalpine) and bare rock (alpine) area, and varying relative cover of lakes (lake abundance). Water samples were taken from the inflow and outflow of the terminal lake of each watershed and analyzed for dissolved nitrogen, dissolved phosphorous, and dissolved organic carbon. Watersheds with high proportions of subalpine relative to alpine were expected to have lower stream water concentrations of nitrogen and phosphorous. Dissolved organic carbon (DOC) concentrations for such watersheds were expected to be higher, reflecting the terrestrial input of leaf litter. Preliminary data from our study suggests that inflow concentrations of total dissolved nitrogen (TDN) are significantly lower in watersheds of high subalpine cover, and significantly higher in watersheds of greater lake abundance. No significant relationship was discovered for outflow concentrations, suggesting that outflow stream chemistry is driven by processes within the lake rather than watershed land cover characteristics. Total dissolved phosphorous and DOC and showed no significant relationship to alpine cover or lake abundance.

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Mar 25th, 11:55 AM Mar 25th, 12:00 PM

Stream Water Chemistry Differences in Watersheds of Varying Land Cover and Lake Abundance

Space Dynamics Laboratory

Evidence is building that atmospheric deposition of anthropogenic inorganic nitrogen and phosphorous is increasing in high elevation watersheds throughout the western United States. Nitrogen released from the burning of fossil fuels and phosphorous released from agricultural lands enters the atmosphere and can be deposited in mountain watersheds via rain and snow. Nitrogen and phosphorous are key limiting nutrients, and therefore even minor increases could have a measurable effect on the oligotrophic lakes and streams within this region. The land cover characteristics of a watershed can have a significant impact on the amount of nitrogen and phosphorous that is released into streams and lakes. Watersheds with relatively low proportions of forest and high proportions of bare rock will leach more nitrogen and phosphorous into surface waters. Heavily forested watersheds will leach less of these nutrients, as they are assimilated by vegetative and microbial processes. Determining the relationship between land cover and stream chemistry within a watershed is useful for understanding the effect of nutrient additions and land use alterations on the ecology of inland waters. Ten watersheds and two subwatersheds within the Sawtooth Mountains of central Idaho were sampled in our study. Each watershed has varying proportions of forested (subalpine) and bare rock (alpine) area, and varying relative cover of lakes (lake abundance). Water samples were taken from the inflow and outflow of the terminal lake of each watershed and analyzed for dissolved nitrogen, dissolved phosphorous, and dissolved organic carbon. Watersheds with high proportions of subalpine relative to alpine were expected to have lower stream water concentrations of nitrogen and phosphorous. Dissolved organic carbon (DOC) concentrations for such watersheds were expected to be higher, reflecting the terrestrial input of leaf litter. Preliminary data from our study suggests that inflow concentrations of total dissolved nitrogen (TDN) are significantly lower in watersheds of high subalpine cover, and significantly higher in watersheds of greater lake abundance. No significant relationship was discovered for outflow concentrations, suggesting that outflow stream chemistry is driven by processes within the lake rather than watershed land cover characteristics. Total dissolved phosphorous and DOC and showed no significant relationship to alpine cover or lake abundance.

https://digitalcommons.usu.edu/runoff/2004/AllPosters/3