Assessment of Farm Dam Impacts on Streamflows
Abstract
This paper discusses the development of a range of techniques required in the assessment of farm dam impacts on streamflows. The use of topographic maps and aerial photography to identify the number and volume of farm dams is discussed, and this includes development of a functional relationship between farm dam surface areas and volume. An essential component required for the estimation of farm dam impacts is the proportion of a dam’s volume used to satisfy demands, and this is investigated using a regional survey of landholders. The development and application of two simulation tools for the estimation of farm dam impacts is also presented. The first model, a Tool for Estimation Dam Impacts (TEDI), is available to assess the changes in streamflows due to farm dams, using farm dam characteristics discussed in this paper. The TEDI model is conceptually simple, but its complexity is commensurate with the nature of available data. The second model (called CHEAT) is conceptually more sophisticated than TEDI, and as a consequence has considerably more demanding data requirements. The paper describes how the sophisticated model is used to evaluate the assumptions in the TEDI model using three test catchments, and limitations of its efficacy are discussed. Finally, farm dam and catchment characteristics derived for 1600 Victorian catchments were used along with previously derived prediction equations to estimate the impacts of farm dams on a range of streamflow indices. The manner in which this regional information can be used to rapidly estimate the impacts of farm dams on specific catchments is discussed and presented.
Authors
Rory Nathan, Lisa Lowe, Robert Morden, Rebecca Lett & Heather Griffith