Declining water levels in the Little Chino Aquifer are causing Del Rio Springs to dry up. The graph below shows that ADWR expects Del Rio Springs to cease flow in 2025. Note that Del Rio Springs is the historical headwaters of the Verde River.
The USGS calculated in 2005 that the Little Chino aquifer contributed about 14% of the base flow of the upper Verde River; thus the overdraft in the Little Chino Aquifer reduces the base flow of the river.
The USGS also calculated that 80-86% of the base flow of the upper Verde River is groundwater from the Big Chino, emerging at Verde Springs (see map below). Groundwater pumping in the Big Chino reduces the base flow by the amount pumped. Unmitigated groundwater pumping threatens the perennial flow of upper Verde River, for the same reason that overdrafts in the Little Chino Aquifer are causing the drying of Del Rio Springs.
The following graph uses data from the USGS Paulden stream gauge at river mile 10. It shows that the lowest 7-day flow in a year has been declining since the mid-1990s. As of June 2020, the base flow is about 15 cubic feet per second, which is approximately 60% of the base flow in the mid-1990s. In 2018 the annual volume flowing past the Paulden gauge was 61% of the estimated flow in 1940. Groundwater pumping and regional drought are the likely causes. Climate change models project higher temperatures and reduced aquifer recharge which will further reduce both base flow and total flow in future decades.
