Delta Mapping With GIS

The long, winding waterways that drain into San Francisco Bay are being mapped and data is being loaded onto a GIS for environmental protection studies.

by / April 30, 1995
May 1995

Level of Gvt.: State, Federal

Function: Environmental protection

Problem/Situation: Too much data on Bay Delta

Solution: GIS helps organize and analyze data

Jurisdiction: California Department of Water Resources

Contact: Dept. Water Resources 916/653-7007.

By Alan Jones

California Department of Water Resources

To study the Northern California Bay-Delta ecosystem in depth and come up with a solution to the multiple and conflicting demands for development and preservation on it is nearly an impossible task - but one the California Department of Water Resources (DWR) must help to accomplish. The Bay-Delta includes rivers and streams which flow from the Sierra Nevada mountains to the Pacific Ocean near San Francisco. Monitoring and managing the huge area requires time, commitment and a new way of managing data with a Geographic Information System (GIS).

DWR's Division of Planning performs a variety of support tasks for Delta studies, including computer modeling, analysis and forecasting. But the data contributed by Planning staff is only a portion of what's available on the Delta and what's needed to tackle the region's difficult dilemmas. The question is how to manage enormous amounts of information from many different sources. To help with this Herculean task, a GIS database on the Bay-Delta ecosystem is being created by the Delta Planning Branch's Environmental Support Section.

"The GIS is one of many evolving tools that will help us manage the mass of complex data available," said Richard Breuer, an environmental specialist in Environmental Support coordinating the development of GIS with the University of California, Berkeley. "The system will help the department in working with other state and federal agencies to resolve Delta problems and make better decisions."

Planners will use this GIS to analyze data, make decisions and support those decisions, prepare environmental impact reports and statements, and monitor environmental mitigation in the Delta. They can import data from other public and private groups to build up the database, as well as add data gathered by DWR staff and other agencies working directly in the Delta, such as the state Department of Fish and Game, the State Lands Commission, and the U.S. Bureau of Reclamation.

"It also contains metadata," Breuer said of the GIS program. "That means the program will not only provide the facts but also the background behind those facts, such as: who collected them, what sampling method was used, are the data current and accurate? Metadata can help establish the credibility and significance of the data to be used for analysis."

Breuer prepared the agreement under which the UC Berkeley Center for Environmental Design Research will help develop the Bay-Delta GIS over the next two years. While several Division of Planning people are already familiar with GIS programs, Berkeley will train additional DWR staff to work with the new GIS.

How GIS Works

GIS works something like the human mind. It can take many sets of data and put them together in different combinations. For a researcher who knows what to look for, it can provide visual displays of the relationship between different data.

The technology, Breuer said, is different from other database systems because spatial, rather than linear, data is collected. Each bit of information - whether about wetland, habitat, distribution of a threatened species, location of a well, or land use - is linked by coordinates to the specific place where it exists in the real world. Features such as waterways, soil types or population density is stored in layers so analysts can pick and choose which data is observed.

GIS is a new way of assembling data and making it universally and instantly available. It's like being able to talk to everybody in the global village at once, and selecting specific individuals in the village to tell you what they know.

If an operator, for example, wants data about Twitchell Island, a few keystrokes and a map of the island appears on the PC or Macintosh. The operator can then call up layer after layer of information - presence of endangered plants, soil type, elevation, roads, wellheads, land use. Each set of data superimposes itself on the screen. The operator can also print out the map, or print out data in various forms, or erase layers and add new ones, such as populations, animal life, housing and Native American artifacts.

Putting together different layers of data will give planners a better way to determine and define relationships. The GIS can combine factors such as time, space, and correlations of data sets, and can "weight" different data to produce a variety of results. From example, land and water use analysts use the GIS to study changes in land use patterns over time. Using maps they created to show these patterns during specific periods, they can ask the system to calculate the changes that have occurred over specific areas.

"The GIS will not only automatically calculate the changes and give you the numerical data," explained Breuer, "the systems will also provide you with a map so you can visually look at the areas of changes."


The Delta, of course, is an extremely complex ecosystem. It is exceedingly important as a major Pacific Coast wetland and a water hub for most of California. The delta also contains cities, industries and farms; includes transportation routes, public services and utilities; and provides recreation. Because information is needed and available on all these areas, the problem becomes one of deciding how much data to include.

"If all the data were input at two-foot intervals, it would require gigabytes of storage and cost millions of dollars. It would get to the point where there was too much information to process," said Breuer. "The task has to be do-able. You have to consider the scale that's needed. For example, it's enough to know the location of a wetland within 30 feet. Surveyors would need higher precision, but for planning issues, that amount of information is more than adequate for our purposes."

GIS Uses

The department is not pioneering with this program. GIS is already used by many local, state and federal agencies including the Army Corps of Engineers and the Soil Conservation Service to analyze Bay-Delta information.

Planning's Land and Water Use Section has been using GIS for two years for spatial analysis of Bay-Delta issues, using a system named GRASS. GRASS, developed by the Corps of Engineers' Construction Engineering Research Laboratory, will be the basis for the Delta Planning work as well. The new system will be able to access, search and download data from UC Berkeley's Center for Environmental Design Research database.

The GIS also holds databases for a number of other DWR programs, including statewide land-use patterns that note changes in agricultural patterns over the decades and rosters of endangered species.

With such a vast database, the GIS will prove its worth beyond its use by the department. In the near future, the system will be accessible to thousands more people via CERES, the California Environmental Resources Evaluation System. CERES, a program of the state Resources Agency, will catalog information about the state's rich and diverse natural and cultural resources and distribute it via the Internet. Using a software program called Mosaic, anyone with access to the Internet can tap into the system, which will also make data accessible from the National Biological Survey and University of California's Sequoia 2000 network.

"All this ready access to such a wealth of information will lead to more informed decision-making," said Breuer. "And for the Delta, it may mean finding some workable long-term solutions that will address all the issues and satisfy all the parties involved."

Reprinted with permission from "DWR News," the newsletter of the California Department of Water Resources.