Special Sessions
Sponsored by the Geomorphology Specialty Group
Association of American Geographers 103rd Annual Meeting
San Francisco, California, April 17-21.

Human Impacts on Watershed Processes 3 - Watershed Management

Paper Session 4301
Friday, 4/20/07, from 12:00 PM - 1:40 PM

Sponsorship(s):

Geomorphology Specialty Group
Water Resources Specialty Group
Spatial Analysis and Modeling Specialty Group

Organizer(s):

Shixiong Hu - East Stroudsburg University
John Faustini - Oregon State University

Chair(s):

William H. Renwick - Miami University

Abstract(s):

• 12:00 AM Author(s):
  *Shuo-sheng Wu - U.S. Geological Survey
  

  Abstract Title: An Exploratory Analysis of the Resolution Effects on AGNPS Runoff Prediction.

  
  

  The purpose of this study is to investigate how the spatial pattern of runoff output from AGNPS watershed modeling changes with input data at different resolutions. Spatial statistics were used to examine whether there is an overall clustering pattern of runoff, where the clusters and hotspots are, how clustering levels and cluster/hotspot locations change with model resolutions, and how the geographic center and dispersion degree of the entire watershed runoff change with resolutions. Variograms were used to investigate the distance of spatial autocorrelation between runoff at different locations. The results showed that the runoff had an overall clustering pattern at all resolution models, and the clustering levels decreased with model resolutions. The distance of spatial autocorrelation increased with model resolutions. The overall clustering level reached maximum at the neighborhood distance of 1920m, while the high-runoff clustering level consistently decreased with the neighborhood distance. The results indicated that cluster locations did not change but cluster sizes decreased with model resolutions. The 210m and 240m resolution models had cluster and hotspot sizes corresponding to visually observed runoff patch sizes and, therefore, were regarded as the most suitable model resolutions for detecting clusters and hotspots among eight tested resolutions. The analyses also revealed that the larger the neighborhood distance, the larger the derived clusters. A neighborhood distance of 960m is considered suitable to identify hotspots through visually comparing with high runoff patches. In addition, the analyses showed that the geographic centers of runoff did not change but the dispersion degree increased with resolutions.

  Keywords: resolution effects, watershed modeling, spatial statistics, cluster analysis, AGNPS

  
  
• 12:20 AM Author(s):
  *Alison Goss - Purdue University
  Laura Bowling - Purdue University
  Jon Harbor - University of Colorado at Denver
  

  Abstract Title: Assessing the Historical Impacts of Landscape Transformation on Water Fluxes, Muskegon River Watershed, MI.

  
  

  The hydrologic impact of land use change has been addressed through numerous studies. Yet, these investigations are limited in their spatial as well as temporal scales because of the lack of high-quality remotely sensed land cover data and streamflow records. Also, this lack of data prevents the complete examination of how water fluxes respond to land use change over decadal and century timescales. Land use/cover change in the Muskegon River Watershed, MI, was reconstructed at ten year timesteps for the past 100 years. These decadal land cover “backcasts” served as inputs to a macroscale hydrologic model, Variable Infiltration Capacity (VIC). Impacts to water fluxes, streamflow, and soil moisture patterns across the watershed will be presented. These results are counter to watershed studies in smaller geographic areas over shorter time periods. This unique type of long-term hydrologic impact assessment, which coincides with periods of widespread industrialization and land use/cover change in a large watershed, enables the creation of mitigation strategies to reduce the negative impacts of development on critical water resources and informs assertions of how land use/cover change may impact water resources in the future.

  Keywords: land use change; water fluxes; Variable Infiltration Capacity (VIC)

  
  
• 12:40 AM Author(s):
  *Martin Roberge - Towson University
  Angela Carlisle - Towson University
  

  Abstract Title: A Comparison of Four Methods for Measuring Impervious Surfaces.

  
  

  Impervious surface coverage (ISC) is a convenient measure of urban land cover for hydrologic research. Asphalt and concrete have a distinctive radiometric signature that is easily identified in remotely sensed imagery. These impervious surfaces impact urban streams preventing infiltration and promoting flash flooding. Empirical research has found high correlations between percent impervious surfaces and hydrologic variables such as rainfall/runoff relationships, flow variability, percent of annual discharge as direct storm flow, and peak storm discharge divided by baseflow discharge. Unfortunately, empirical studies of urban impacts frequently cannot be compared to one another due to differing methods for estimating ISC. This study compares four methods for estimating ISC over a variety of scales and land uses. Results indicate that planimetric methods (building outlines and edge-of-pavement digitized from airphotos) consistently underestimate ISC at urban sites. Two Landsat methods (supervised classification and the regression tree methods used in the National Land Cover Dataset) underestimate ISC at rural sites under 10% imperviousness. Land use methods (multiplying land use map polygons with published percent ISC factors) produce highly variable estimates of imperviousness due in part to intensity of land use. These findings may have implications for stormwater regulations. Permit applicants will base their estimates of impervious cover on site diagrams, producing a low estimate of ISC similar to planimetric methods. However, regulations may be based on scientific literature that uses other methods of ISC estimation. These other methods will produce higher estimates of imperviousness. The end result will produce ordinances that are less effective than intended.

  Keywords: impervious surfaces, stormwater regulation, urban impacts

  
  
• 1:00 PM Author(s):
  *Geoffrey T. Klise - Sandia National Laboratories
  Carlos A. Aragon - New Mexico Institute of Mining and Technology
  

  Abstract Title: Using GIS and System Dynamics Software to Model how Changes in Land Use and Cover will affect Discharge in Ungauged Tributaries in the Gila and San Francisco Basins.

  
  

  As part of the 2004 Arizona Water Settlements Act, southwestern New Mexico has an opportunity to utilize up to 14,000 acre-feet of water annually from the Gila and San Francisco Rivers, with the constraints that stream flows must meet requirements of the Consumptive Use and Forbearance Agreement (CUFA) and comply with the federal Endangered Species Act. To evaluate potential impacts on stream flow from alternative water resource development scenarios, a collaborative team of stakeholders from the region is working with Sandia National Laboratories and the New Mexico Interstate Stream Commission to develop a basin-wide surface and ground water model. Integral to the model is discharge from tributary watersheds, a majority of which are ungauged. Using both geographic information system (GIS) and system dynamics software, we are able to recreate past rainfall-runoff events based on a modified Variable Infiltration Capacity model. Stakeholders on the modeling team would like to see the differences in river discharge as a result of changes in land use and/or land cover. The watershed model will allow users to change the spatial and temporal aspects of land use and cover and see if the projected or altered hydrograph passes or fails the required CUFA tests. The output from this effort will be one of many tools that can then be used by stakeholders to determine how the New Mexico Unit should proceed with the available water.

  Keywords: watershed modeling, GIS, system dynamics, land use, Variable Infiltration Capacity, New Mexico, Arizona

  
  
• 1:20 PM Author(s):
  *Christopher Brown - New Mexico State University
  Quita Ortiz - New Mexico State University
  

  Abstract Title: The Impacts of Land Use Change on Water Resources and Traditional Acequia Culture in North Central New Mexico.

  
  

  Rural areas throughout the western United States are undergoing rapid and far-reaching land use changes that impact water management, riparian ecosystems, and traditional cultures. Impacts to water resource use and management include: potential risks of groundwater contamination due to increased numbers of single household septic systems, potential overdraft of groundwater resources, surface water quality impacts, and changes in the distribution of water supplies from agricultural to municipal/industrial uses. In northern New Mexico, the acequia water use regime and attendant acequia-related cultural values are at particular risk due to increasing urbanization pressures and the potential impacts on actual water use, water quality, and riparian vegetation along irrigation ditches and streams. GIS, remote sensing, and aerial photography interpretation techniques are used to create a series of land use change maps to assess the impacts of critical water resources and local communities along the Black Mesa Reach of the Upper Rio Grande Basin. Land use maps we generate depict changes in water resource use and management, risks to groundwater, changes in acequia management and water use, and riparian ecosystem impacts. This project provides insight to local and state planning programs with constructive methods for further research, and is also applicable to other western states with similar challenges.

  Keywords: Water resources, Acequias, land Use Change

  
  

Session Description: Human impacts are pervasive across the modern landscape. Land use, resource extraction, and other human activities alter vegetation cover and species distributions; alter surface topography and disrupt soil layers; move large quantities of rock, soil and other materials; re-route surface and subsurface water flows; and directly or indirectly introduce large quantities of chemicals across the landscape, among other impacts. These many impacts affect key watershed processes even in relatively remote areas, altering the routing and delivery of water, sediment, organic matter, and dissolved chemicals to rivers and streams and in turn altering channel and floodplain morphology, aquatic habitat quality, and riparian ecosystem structure and function. Because humans depend upon watersheds for water supply, recreation, and many ecosystem services, understanding and management of human impacts on watershed processes is profoundly important to human societies. This series of sessions explores human impacts to hydrogeomorphic, biogeochemical, and ecological systems and processes in watersheds in a range of environments. Primary focus areas include (1) mountain watersheds; (2) geochemistry, water quality, and nutrients; (3) watershed management, particularly with respect to streamflow and fluvial processes in urbanizing landscapes; and (4) ecological impacts and processes.