Saied Tadayon: I’m Saied Tadayon; I’m a hydrologist and have been working with the Arizona Water Science Center since 1990. One of the projects I’ve been working here over the years is water use, and we have been complying water use for Arizona by county and hydrologic unit code for many categories such as: irrigation, municipal, mining, thermo, industrial, waste water.

Dylan Cobean: Basically any way that water is used in a state; we would need to look into that, but mainly what we’ve focused on for the time I’ve worked on the project is agricultural and some thermoelectric and public supply. Saied Tadayon: Agriculture is using most of the water in Arizona and we could say that about at least 80% of water withdrawals have been used for growing crops in many parts of the state.

Brandon Forbes: This is an example of one of our field verification maps that we would take out into the field. This map was digitized in ARC-Map and all these parcels are boundaries of active or nonnative fields in the Douglas area. They are color coded by crop type so that when we visit them we know if something has changed. Dylan Cobean: So each piece of farm land has a given crop and a given irrigation system on it. If we know the crop and the irrigation system, we can determine how much water and how efficient that water is being applied to the crop, from that you can get an irrigation withdrawal.

Saied Tadayon: We use a variety of irrigation systems to irrigate those fields. The primary ones are surface water, which is flooding, or sprinkler. And it could be a different type of sprinkler: lateral or center pivot, and also drip irrigation. Dylan Cobean: So here we are on an alfalfa field fed by flood irrigation. Flood irrigation roughly has a system efficiency of 50 to 60%. Most of those loses are due to either evaporation or leakage along the canal system.

Brandon Forbes: Historically in the West, Arizona included, farmers would irrigate with flood irrigation. This is an example of an old irrigation ditch that’s no longer in use. Farmers have now changed to sprinkler, and center pivot irrigation systems to raise efficiency, which decreases water use and increases water efficiency. This is an example of center pivot irrigating corn. The efficiency can be affected by how high the sprinkler heads are put off the field. As you can see behind me, the sprinkler heads are quite higher than the corn that it’s irrigating and this will increase the effect that wind can have on the water and also increase potential evaporation which can lower overall irrigation system efficiency.

Dylan Cobean: So here we are on an apple orchard fed by drip irrigation, we know it’s on drip irrigation by these irrigation lines that run along the apple orchard. This is easily the most efficient form of irrigation to be used on crop, the reason why is it applies the water most directly to the crop.

Saied Tadayon: The economy development of the state of Arizona, is largely influenced by adequate water supply, and documenting the trends in water use and developing water use data bases are very important.