Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2011
Publication Date: 4/21/2011
Publication URL: http://handle.nal.usda.gov/10113/54480
Citation: Cao, H., Vervoort, R.W., Dabney, S.M. 2011. Variation in curve numbers derived from plot runoff data for New South Wales (Australia). Hydrological Processes. 25:3774-3789. Interpretive Summary: The curve number method is a simple rainfall runoff model that remains a widely used tool for predicting runoff when detailed data is not available. This study characterizes the range of agricultural treatments across a large spatial area in the state of New South Wales, Australia. The data used for the analysis spans several decades of rainfall and runoff observations. Several different derivation methods of estimating the CN were compared. Systematic variations in the curve number were observed due to land use, soil moisture content, and rainfall depth. Based on the analysis a table of curve number values for different land uses is presented that will provide guidance for rainfall runoff modeling studies in the agricultural important areas of New South Wales.
Technical Abstract: The curve number method is a simple one parameter (the curve number) rainfall runoff model. While its theoretical underpinning has been questioned it remains a powerful hydrological tool in the absence of detailed data and is therefore used extensively in hydrological models. This study aims to characterize the variation in maximum retention values (S), which underlie curve numbers, for a range of agricultural treatments across a large spatial area in NSW (Australia). The data used for the analysis spans several decades of rainfall runoff observations. A range of different derivation methods result in variation in mean and variance of S. In particular, methods that emphasize the larger storms result in greater S and thus lower runoff. For larger spatial scales, emphasis on larger storms gives more reliable estimates of S. Systematic variation in S arises from variations in treatment, pre-runoff soil moisture, rainfall depth and variations in cover. Based on the analysis a table of curve number values for different land uses found in NSW is presented. The resulting distributions of S and curve numbers provide guidance for rainfall runoff modeling studies in the agricultural important areas of NSW.