California’s surface water resources consist of a network of reservoirs, rivers, canals and estuaries. Each of these supports a distinctive aquatic ecosystem that relies on the availability of freshwater, and they are all environmentally threatened. In order to establish equal footing for aquatic ecosystems in the political discussions of water policy, new tools for sensing and modeling must be developed. We are using these tools for monitoring the ecosystems of lakes and estuaries, starting with Lake Tahoe and the smaller estuary systems along the outer coast of California. UC Davis has amassed a huge ecological data set for Lake Tahoe spanning over 40 years, during which there have been major environmental and ecological changes. By combining the historical data with real-time information, we plan to create models and tools that examine the link between water quality and fish behavior.