Back in the 1980s, the University of Arizona operated a research facility near Oracle, AZ, investigating water harvesting and runoff farming. One of the products of their research was a Primer on Water Harvesting and Runoff Farming written by Gerald Matlock and Gordon Dutt. The authors were predicting the widespread adoption of water harvesting for agriculture as early as 1965, a prediction that has yet to be realized. The primer contains calculations of water yields under various conditions and the relation to yields of various crops. It also contains a guide to design and construction of water harvesting systems and to calculating catchment-to-cultivated area ratio. Manuals on arid and semi-arid water harvesting that contain the same level of detail are rare, so this primer may still be useful for water harvesters.