July 20, 2001 Research Subcommittee Committee on Science U.S. House of Representatives Washington, D.C. Re: Need for Real-time Data in the Modeling of Watersheds Dear Honorable Members: I am writing to you in support of the HPWREN project as a user of the infrastructure provided by HPWREN. I would like to briefly describe how my colleagues and I plan to use the HPWREN to benefit our research efforts as well as to benefit the management of water quality in San Diego County and possibly throughout California. We are working to develop a new and systematic method of modeling urban watersheds with a special interest in coastal areas. A particular challenge in this work, and an aspect that makes it especially interesting to other parts of the world, is the general lack of information within San Diego County regarding surfacewater flow. To overcome this limitation we are developing methods to extract the basic structural watershed information from synoptic data sources provided by the United States Geological Survey. The same information is available for most of the contiguous United States and therefore our method is applicable to many other parts of the country. The coastal areas are particularly interesting because the ocean is the ultimate receiving water for most non-point source runoff in highly urbanized areas. In addition to pollutants contained in watershed output, there is also fresh water flowing from the continent. In order to understand the mass balance of the hydrologic cycle, it is necessary to have an estimate of the total fresh water being delivered to the ocean. Watershed models are a way to develop these estimates. In collaboration with the San Diego County Stormwater Management Department, we selected Los Penasquitos Lagoon to conduct our pilot study and develop the data sources and methods to support modeling of other arbitrarily-located watersheds. Soon we hope to apply this methodology to the watershed of the Santa Margarita River as well in collaboration with San Diego State University, the HPWREN project, and the Center for The Coastal Environment at Scripps Institution of Oceanography. At present, we have a preliminary watershed model for Los Penasquitos lagoon, just north of La Jolla, and a general methodology for estimating and predicting stormwater runoff. For such models to be useful, they must be calibrated frequently enough to ensure that changes to streambeds and engineering changes within the watershed are being accurately reflected in the model's structure and predictions. This requires data on stream flow, precipitation within the watershed, and temperature. We need a reliable and long-term record of the flows within the streams we are modeling and this requires real-time data recording. In this context, real-time means fast enough to keep up with natural processes such as regional and localized storms as well as residential, municipal, industrial and agricultural runoff. These data must be relayed via a network and stored in a data system where the modeler can use them for assimilation in model development and calibration as well as during the execution of the model for use in nowcasting and forecasting. Hindcasting also requires a data record collected in real-time although analyzed by post facto model runs. Preliminary research reveals that appropriately placed video or still cameras, with wireless modems for data transmission, within site of fixed structures, such as culverts, can provide water level estimates from images. These can be used to estimate flow, and therefore volume, over time. This approach should be relatively inexpensive; on the order of $1000-2000 per location in contrast with an annual cost of about $10,000 per stream gauge station using conventional methods. The wireless backbone needed for data transmission can be from the infrastructure being provided by HPWREN. In addition, we need to have data acquired by meteorological stations for precipitation, evaporation rates, wind and temperature. We have plans to deploy a test site with this configuration in the Santa Margarita Ecological Reserve, operated by San Diego State University, over the next six months using the HPWREN infrastructure. Sincerely, John Helly Senior Scientist email: hellyj@ucsd.edu