Irrigation canals form a sort of circulatory system for global agriculture. Across the world, millions of kilometers of human-made canals carry water from lakes, rivers and reservoirs downhill to farmland. Canals are vitally important to human food production, yet many agricultural areas lack the means to monitor the ebb and flow of water through these waterways. This forces farmers and water managers to rely on scattered gauges, inspections and local reports to make decisions about water use.