Water flowing in the Verde River comes from 1) surface runoff from rain and snowmelt and 2) groundwater that springs and seeps release into the river and its perennial tributaries. If the river had to rely on rain and snowmelt runoff alone, it would be dry much of the year. This vital groundwater supplies about half the Verde River’s annual stream flow; it alone maintains the river’s year-round flow. Without it, the river would flow only after periods of rain or snowmelt; its channel would be dry most of the year. Over-pumping of groundwater elsewhere in Arizona has dried up numerous other rivers that once carried water year round. https://verderiver.org/wp-content/uploads/2017/11/wrn-1-a-desert-treasure-at-risk-1.pdf
Prior to concentrated human settlement with wells and other water infrastructure, the interconnected system of groundwater and surface water was balanced with the quantity of water seeping into aquifers and the amount of water seeping out through springs and into streams. Wells disrupt that long-term natural balance since pumping of wells can intercept groundwater that was en route to springs and streams. Pumping also can deplete groundwater beneath the riverbed, although distant from the wells, causing water to flow away from the river into the groundwater.
The movement of groundwater is much slower than the movement of water flowing on the surface; thus the effect on stream flow from the pumping of groundwater doesn’t show up immediately. But, inevitably and eventually, the component of groundwater that contributes to stream flow is reduced by an amount nearly equal to the consumption of water pumped from wells.
Substantial groundwater pumping in the Verde River basin began in the late 1930’s, mainly for irrigation. Today, groundwater pumped from thousands of wells in the basin provides essentially all the water for human usage: drinking, cooking, washing, toilet flushing, landscaping, industrial and municipal uses, and still some agricultural irrigation. A significant exception is that nearly all agricultural irrigation in the Verde Valley is supplied by water diverted directly from the Verde River and its perennial tributaries.
The unavoidable effect is that as the growing population continues to use groundwater, the Verde River, or at least substantial parts of it, will become another Arizona dry wash flowing only briefly in response to storms or snowmelt.
Since Verde Valley residents and businesses rely almost entirely on groundwater for domestic water needs, the long-term existence of the basin’s water resources is at risk due to increased groundwater pumping, a high dependence on groundwater, the potential development of the vast amount of private land currently undeveloped, Arizona water laws that do not adequately protect surface water, and the lack of regional water planning.