Drought Information Banner

Drought Tools and Methods

Here you will find tools and methods the State Water Board is developing to support drought decision-making. These resources will be updated periodically, so please check back regularly for updates or subscribe to our email list by filling in the form at the bottom of the main drought page.


Sacramento - San Joaquin Watershed Graph

Water Unavailability Methodology for the Delta Watershed (May 2021)

The State Water Board is updating its methodology for evaluating water unavailability in the Sacramento-San Joaquin Delta watershed.  The updated methodology uses best available data to determine when water supplies are not available for diversion based on priority of right, and improves upon methods used in prior droughts.  The State Water Board plans to use this methodology to issue notices of water unavailability as early as June 2021.


Water Supply Demand Tool graph

Water Supply and Demand Visualization Tool (April 2021)

The Water Supply and Demand Visualization Tool is intended for informational purposes and will not be used to make water allocation or shortage decisions.  This interactive tool shows basic monthly water balance data for past years in major watersheds throughout California at the HUC-8 (~700 square miles) scale. The tool allows users to compare different water supply and demand scenarios side-by-side, includes an interactive map of diversion points, and provides a detailed list of all water rights within the user-selected watershed. The State Water Board will add more watersheds and improve ease of use in the coming months.

As we continue to develop this tool, we want your feedback; please submit your ideas by visiting the tool clicking on the “About/Help” tab at the top of the page, and selecting “Report Bugs/Data Issues” from the dropdown menu.

  See our Frequently Asked Questions for more on the Water Supply Demand Visualization Tool. 


Computer with water drop containing 1's and 0's

Water Demand Data Assessment (Coming May 2021)

The State Water Board is conducting a Water Demand Data Assessment to address data quality issues and improve how water use data is collected, reviewed, and processed. Water right holders are required to report how much water they use each year, but the reports we receive vary in terms of quality, making it difficult to incorporate the data into watershed-scale planning. The State Water Board is streamlining how we compile and review this data and developing a set of protocols and requirements to process the data. The end product will be a uniform process that can be applied to water use data collected throughout the state by the State Water Board’s Division of Water Rights. This will include documented methods and code scripts that automate cleaning and revision of erroneous data as well as flag other data for correction.


Dam with water spillover over it

Initial Hydrology Modeling (Coming Fall 2021)

The State Water Board is developing tools and methods to estimate yearly hydrology, create an initial planning forecast, and evaluate water supply at the sub-watershed scale. Components will consist of a tool that models initial supply conditions at a watershed scale in the Eel River and the Russian River, and a report that documents and standardizes the steps, processes, and datasets (and sources) used to model supply.


Water Pipeline

Water Allocation Tool (Coming Fall 2021)

The State Water Board is expanding the UC Davis Drought Water Right Allocation Tool (DWRAT) to better incorporate geography, supply, and priority into curtailment decisions. This expanded tool will incorporate other ongoing efforts, including the Water Demand Data Assessment and Initial Hydrology Modeling methods. This tool will be piloted in the Eel River and tested in broader settings.


  We value your feedback on these tools.

See our Calendar of Events for upcoming workshops where these tools will be demonstrated and discussed, or reach out to drought@waterboards.ca.gov with input.