Two years of drought have stolen much of Idaho's groundwater supplies, although increased usage of the aquifer for farming has had longer lasting effects, Idaho Water Resources Department officials say.

Lack of winter snow and spring rains reduced the recharge of shallower aquifers. They, in turn, feed the deeper groundwater systems.A smaller snowpack left less irrigation water in canals. A portion of that water seeps out of the ditches and recharges the groundwater.

Irrigators also began using water earlier in the spring and later in the fall, removing higher than normal amounts of water.

All those trends became evident in test wells monitored this year by the U.S. Geological Survey. By looking at the spring levels in the wells, it indicated that the groundwater has experienced long-term declines in some areas of the state.