But growers point out that the movement of underground water changes for many reasons and that it is difficult to identify the causes, including whether new vineyards are a factor. Some industry representatives also say the groundwater taken by many new vineyards is less than what might be pumped for a home built on the same property. Erosion is another major issue. A small patch of forest provides thousands of trees, bushes, grasses and weeds that all act to hold topsoil in place during winter storms. Removal of the vegetation, experts say, results in a tremendous increase in downstream runoff.
Higher runoff can result in more sediment in streams and creeks.
Too much sediment in the streams can pose problems for spawning fish. Sediment buildup also has been cited as a major contributor to downstream flooding. Growers say the concerns of biologists and conservationists are overstated, and that increasingly, vineyards are being designed to soften or eliminate most major environmental impacts. For example, Kendall Jackson's vineyard in Bennett Valley, running up the east side of Taylor Mountain, has been developed without the removal of a single tree. Big parts of the former Friedman Family Ranch have been left untouched to provide habitat for the mountain's wildlife, which includes blacktail deer, wild turkeys and bobcats.