An ecologist installed an extensive soil moisture sensor network to study the effect of slope orientation on plant available water. He collected reams of soil moisture data, but ultimately he was frustrated because he couldn’t tell how much of the water was available to plants. He’s not alone in his frustration. Accurate, inexpensive soil moisture sensors have made soil moisture a justifiably popular measurement, but as many people have discovered, a good hammer doesn’t make every soil water problem a nail. Water content can only show how much water there is. Hydraulic conductivity shows how fast water can move. But water potential shows whether it will move and where it’s going to go. Click on the links below for a comprehensive look at the science behind water potential measurement.