In Solano County, near Sacramento, [Alex] Johnson is working on what he says could be a model for parched ag regions around the state. … Last month, working with IBM and a company called SweetSense, Johnson’s team began deploying simple, solar-powered sensors, originally developed to monitor creaky groundwater pumps in East Africa. The sensors will be used to detect how much water is flowing in real-time. … Farmers will use that data to trade their water on (what else?) a blockchain platform.