Fighting over water is a popular sport in the West, where generations of lawyers have refined the practice until it approaches an art. Often, the quantities at stake are prodigious, the output of entire watersheds. In other instances, however, the volume is so minuscule as to leave outsiders puzzled by all the fuss. A dispute of the latter sort is threatening to break out in Ventura County, where a broad coalition has united behind one of the largest dam-removal projects in American history.