California's Water Plan, prepared by the state Department of Water Resources and currently being updated, always seems to imply that our supply of water to support development is endless. Clearly, all of our water problems are exacerbated by development. But the California Water Plan never addresses the crucial questions of what are the limits on our supply of water and what is the ultimate population that can be supported.

Current law says the state must prepare a Regional Housing Needs Assessment that requires local governments to provide their "fair share" of housing of various types to accommodate the state's population projections. Unfortunately, our water purveyors always seem to step up blindly and say they can supply the necessary water. If this is true, then why is there a growing cry for conservation and current threats of water cutbacks?

If there is not an endless supply of water, at some point there will not be enough water to support additional development. For example, note the agriculture water cutback now projected for 2008. Inevitably, we really will run out of water, and the state's policy on endless housing to support further population growth will have to be redefined. At some point, "the inn" will be full!

The California Water Plan needs to address this crucial issue now. We need a "water carrying-capacity analysis" to determine what our limiting water supply really is. Then we can analyze the impacts on housing and population. This will enable us to properly plan for the future of our state. Population growth is not an immutable fact of life.

What is our water availability?

Southern California gets its water from three sources: the Colorado River, Northern California and local groundwater (percolated rain/snow/runoff).

Our share of Colorado River water has already been greatly reduced and probably will be cut more in the future. Water from the north is constantly impacted by lawsuits, environmental requirements and the weather, as is the amount of water we get from the ground. All of these sources produce finite amounts of water.

"New sources of water" are often promoted as the answer, but in fact they are only a redistribution of existing water sources. Conservation is always good but limited in amount. Recycling and desalinization offer the promise of additional water but currently are more expensive than other sources, particularly desalinization. Taking water away from agriculture and/or the environment for urban uses is also possible but reduces our agricultural output and will damage our environment. How much of our agriculture and environment are we willing to destroy?

Some people say that the answer is simple: Just build more reservoirs and store the water that runs to the ocean from our streams and rivers. However, they fail to acknowledge that this water is mandated by law for environmental protection. So where will we (reliably) get the new water to put in the new reservoirs?

Since California's population is projected to increase 30 percent by 2025, where is the 30 percent increase in our water supply coming from?

Also, the reality of global warming is that droughts will be more frequent and of longer duration. How are we going to get a sustainable supply of water to support endless development?

We need to plan!

Obviously, our supply of water is limited. So the crucial questions remain: What is our limiting supply of water, how will it be allocated and how much population can it support?

Our planners need to address this critical issue. If our planners choose to ignore this issue, then who is looking out for the future of California and for all of us who live here?

Bonsall resident Gerald R. Walson is president of Bonsall Area for a Rural Community, a local group. In March, he was elected as Division 1 director for the Rainbow Municipal Water District, which has more than 7,200 customers in Rainbow, Bonsall and parts of Fallbrook.