Thursday, August 9, 2007

PS 67-147: Remote sensing techniques for non-point source pollution assessment

Benjamin M. Holcomb1, Jane McAtty1, and Brian Kasper2. (1) Nez Perce Tribe, (2) Watershed Sciences, Inc.

Total Maximum Daily Loads (TMDLs) were developed on 12 watersheds in the Lower Clearwater River Sub-basin on the Nez Perce Reservation in north-central Idaho. The reservation land use is comprised of 52% agriculture (primarily dry-land wheat) and 28% forest.  Temperature and sediment are the most influential pollutant parameters affecting the designated beneficial uses of reservation streams. However, these parameters are the most challenging to assess the load distribution and concentration within a watershed.  Thus, in order to effectively restore beneficial uses and to provide tools for measuring implementation performance, remotely-sensed, nonpoint source pollution assessments were utilized.  Longitudinal temperature profiles were generated from thermal infrared imaging (TIR) on 235 miles of streams between 2004 and 2005.  Light Detection and Ranging (LiDAR) imaging was collected on ~180,000 acres to provide 1 meter resolution mapping of near stream vegetation canopy coverage, stream morphology, and topographic shade angles.  Combined, these data collection methods predicted potential vegetation shade values and stream segment locations that would create effective thermal reductions in the watersheds.  A sediment source assessment using a GIS-based Revised Universal Soil Loss Equation (RUSLE) model was employed to determine specific erosion rates and locations within each watershed.  This model proved useful in: 1) identifying local erosion “hotspots”, 2) predicting sediment delivery, and 3) measuring land management techniques.  By using the latest nonpoint source pollution assessment technologies, local land management agencies and landowners can efficiently restore these watersheds to their beneficial uses.