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United States Department of Agriculture

Agricultural Research Service

Title: Assessing Scale Issues on Semi-Arid Watersheds with a Multi-Attributed Decision Support System 1236

Authors
item Weltz, Mark
item Kidwell, Mary
item Fox, H - NRCS
item Yakowitz, Diana

Submitted to: International Rangeland Congress
Publication Type: Proceedings
Publication Acceptance Date: January 13, 1999
Publication Date: January 13, 1999

Interpretive Summary: A new Rangeland Health methodology is increasingly being used by Federal land management agencies to evaluate the sustainability of rangeland ecosystems. It is necessary to understand the scale at which the assessments are applicable and to develop methods for aggregating results to larger areas. A multiple objective decision support system (MODSS) is used to evaluate Rangeland Health assessment scores from four small semi-arid watersheds, each with a different management/treatment scenario, within the Santa Rita Experimental Range in southeastern Arizona, U.S.A. The MODSS is valuable for examining land areas from numerous, often conflicting, decision-making viewpoints or from input provided from multiple decision-makers. Three classes of land types, based on hydrologic properties, are identified within each watershed. Four methods for analyzing the relative contribution of the assessment scores obtained for each land type are applied to determine an overall rating for each watershed. Surface runoff, sediment yield, and vegetation data collected over a 23 year period provide a quantitative measure to compare the overall rating resulting from the four weighting methods. Results indicate that a method based on both area and physical processes best reflect the direction of change seen in measured data.

Technical Abstract: The concept of Rangeland Health provides a framework for an emerging assessment methodology developed by land management agencies to evaluate the sustainability of rangeland ecosystems. A multiple objective decision support system (DSS) is used to evaluate the scale at which Rangeland Health assessments are performed for four watersheds, each with a different tmanagement/treatment scenario. Three classes of land types within each watershed (diffuse uplands, contributing flow paths, and gullies) are evaluated. Four different methods for analyzing the relative contribution of the assessment scores obtained for each land type are applied to determine one overall rating. Surface runoff, sediment yield, and vegetation data collected over a 23-year period provide a quantitative measure to compare the overall rating results from the DSS. Seventeen individual attributes are allocated to one or more of three categories within the DSS: watershed function; distribution of nutrient cycling and energy flow; and recovery mechanisms. Each attribute is assigned an importance order within a category independent of its ranking in another category. A Algorithms based on linear and dynamic programming are implemented in a computer spreadsheet compute the range of ratings from most optimistic to most pessimistic. The DSS is valuable for examining land areas from numerous, often conflicting, decision-making viewpoints.

Last Modified: 10/30/2014
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