Abstract

  
  When we examine sediment quality in aquatic ecosystems, we typically look at systems such as rivers, lakes, estuaries, or impoundments whose sediments originated elsewhere. Although we may be able to characterize some aspects of sediment fate and transport, we are not able to effectively forecast or hind-cast without an understanding of external sediment loads to the system. So, we must model sediments entering the system from its contributing watershed.

  In this paper, we will look at three tools used in different studies to quantify sediment loads originating in the watershed, and discuss the pros and cons of each approach. The three tools to be discussed are:

• Statistical estimation. Sediment loads from tributaries to Green Bay were estimated using a statistical model relating flows and concentrations.
• SWAT - Sediment loads to the Lower Fox River were modeled with the Soil and Water Assessment Tool, a river basin scale model used to quantify the impact of land management practices in large, complex watersheds.
• HSPF - The BASINS/NPSM implementation of the Hydrologic Simulation Program - Fortran HSPF was used to model sediment wash-off and in-stream scour in a small urban watershed in Georgia.

  The discussion will touch on each tool's capabilities to model different types of solids, and on some of the details of bringing the watershed loads into the aquatic model used. These details include sediment characteristics, translation of spatial and temporal scales, and calibration. General conclusions and recommendations for selection and linking of appropriate watershed models will also be presented.