A Spatially Explicit Method for Determining the

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A Spatially Explicit Method for Determining the
Effects of Watershed Scale Land Use on Stream
Conditions by Jon Kehmeier For
partial fulfillment of the degree of Master of
Science in Bioresource Engineering
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Study Objectives

• Identify and quantify the impacts that various
  land use practices have on native fish
• Develop a method that accounts for complexity of
  agricultural watersheds

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Site Selection

• Identified 142 agricultural basins
• Rank based on percentage of each agricultural
  land in basin
• Ag Row Crop, Annual Grass, Perennial Grass
  Orchard/Berry, Pasture
• Non-Ag Urban, Riparian/Wetland, Forest
• Develop histograms based on ranks

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Sampling Efforts

• Backpack Electrofishing
• In-stream habitat evaluation
• Terrestrial land use evaluation

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Model Development

• Assumptions
• Each land use has a unique and measurable effect
  on stream fish communities
• All portions of a basin have an impact
• Land use near the sampled reach has larger impact
• Response of fish community is a function of
  upstream landscape

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Model Development

• Grid Development
• Land Use/Land Cover (LULC) grid
• Flow direction grid
• Stream network grid
• Use for development of algorithms to determine
  cell-specific flow paths

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Model Development

• Compute lengths of flow paths
• Total distance
• In-stream distance Out-of-stream distance

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Model Development

• Influence of one land use cell
• Sum Icells for each land use in a watershed and
  use sum as influence measure of that land use

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Row Crops
Ann. Grass
Per. Grass
Orch/Berry
Pasture
Urban
Riparian
Forest
Streams
Sampled Reach
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Sampled Reach
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Sampled Reach
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Sampled Reach
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Model Development

• Total distance model (TLU)

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Model Development

• In-stream/Out-of-Stream (InOut) Model

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Results

• Analysis showed no evidence of annual variations
  within replicated sites
• Biomass of native benthic dwelling fish most
  significant response
• Model using squared in-stream and out-of-stream
  metrics most successful

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Interpretation of InOut-2 Coefficients
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Discussion of Model Coefficients

• Instream row crop
• Increased runoff / baseflows
• Eutrophication
• Instream grass metric
• Surface roughness
• Mimics natural vegetation
• Out of stream annual grass
• Autumn disturbance

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Discussion of Model Coefficients

• Out of stream urban
• Flashy runoff events
• Silt and organic substrates
• Loss of habitat

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