This report documents the results of a study of the cost-effectiveness of the stream-gaging program in Iowa. Data uses and funding sources were identified for the 122 surface-water stations (including reservoir, lake, stage only, and miscellaneous stations) operated by the U. S. Geological Survey in Iowa. There are 110 continuous streamflow stations currently being operated in Iowa with an annual budget of $592,000.
The average standard error of estimation in continuous streamflow records is 11.4 percent. It was shown that this overall degree of accuracy at the 110 continuous streamflow stations could be improved to 10.5 percent if the gaging schedule was optimized.
A minimum budget of $543,000 is required to operate the present streamgaging program in Iowa. With this budget, routine visits to gages would be decreased to five during the open-water season and three during the winter. A budget less than this does not permit proper maintenance of the gages and recorders. At the minimum budget, the average standard error would be 12.5 percent. The maximum budget analyzed was $1,235,000, which resulted in an average standard error of 4.2 percent. A 10 percent increase in the current budget to $656,000 would result in a standard error of 8.4 percent.
There are still a few basins with drainage areas greater than 200 square miles that have no continuous streamflow data. Continuous streamflow gages need to be established in these basins as funds become available. All stations in the current program need to be maintained for the forseeable future.
Data simulated by using the flow-routing and regression methods for stations in 6 river basins do not meet the accuracy required for their data use. Other basins will be studied later to determine if alternative methods to meet accuracy standards are feasible.
