In addition, the lava is cracked, leaving large spaces through which water can flow. Farmers depend on the aquifer to irrigate over one million acres annually. Most farms also depend on wells for domestic and stock water. In addition, over 41 communities serving 127,000 people utilize the aquifer for municipal water supplies, either from wells or springs. The aquifer lies approximately 1,000 feet below the surface and flows slowly, following the gradual slope of the Snake River Plain.
Streams entering the lava plain, rain, and snow melt all disappear into the porous rock.
The water then makes its slow journey southwestward, eventually cascading from the canyon walls into the Snake River at Thousand Springs. In 1992, researchers began an Aquatic Resources Assessment at Craters of the Moon. The study collected baseline data on water and ice in the Monument. It also documented the physical condition of the streams and chemical content of the water in streams, water holes, ice caves, and wells. In addition, researchers examined the invertebrate animal life of streams, and they reviewed historical documents for any trends in water quantity.