In the past, the district had been unable to supply golf courses with all the recycled water they needed for irrigation, especially in the summer.Assuming the golf courses paid the $70 million (!), this pipeline will increase "permanent supply," which will also increase demand. How? Before the pipeline, pumping would rise and fall with the season (and gas prices); with the pipeline, a fixed amount of water can be had at a low cost (besides the $70 million) that is unlikely to rise and fall with local conditions. If, for example, water supplies are tight, water authorities will not be able to increase pumping prices (via taxes) to reduce the quantity demanded.
When there's not enough recycled water available, golf courses have to use groundwater - the valley's drinking water - for irrigation
Bottom Line: This project -- by reducing the options for responding to changing conditions of supply and demand -- will not only fail to "fix" supply problems but will also make a crisis more-likely: When a supply shock does eventually hit, demand will be higher than now and stressed supplies will not not be able to respond (at all/fast enough) to mitigate damage. (But those golfers will sure have a good time!)