Connections Between Surface And Groundwater

During the drought years of the mid-1950s, farmers in Nebraska and other states flocked to the offices of geologic surveys to find out if they had water under their land. Manyhem and that the new technologies in well drilling, turbine pumps, gated pipes and center pivots made irrigation possible. were pleasantly surprised to find out there was water under t

It must have seemed like a miracle, and the miracle produced an irrigation boom. Many farmers began to look at irrigation from groundwater sources as a right – they owned the land, and they should own the water under it, too. Groundwater quickly became essential to farming operations all across the country.

Yet, at around the same time, seemingly unrelated events occurred that would put limits on the sense of entitlement that farmers had in groundwater.

In 1952, President Harry Truman designated 40 acres of federal desert land in western Nevada as a national monument. The land surrounded a strange underground pool known as “Devil’s Hole.” On the surface, the hole is only six-feet wide by 18-feet long. But below the surface is a pool more than 300 feet deep. Actually, the pool is a cave filled with warm 86ºF groundwater. In that pool is a unique species of fish, the Devil’s Hole pupfish, that has been evolving, isolated in that pool for more than 10,000 years. This species exists only in this pool. In 1952, it was estimated there were only 350 pupfish left.

In the 1960s, the huge, 12,000-acre Cappaert Ranch that surrounded Devil’s Pool sunk an irrigation well 2½ miles from the pool. Water levels in the pool began falling almost immediately, and biologists studying the pupfish realized that they spawned on a moss-covered shelf near the top. If the water dropped below this shelf, the moss would die and the pupfish wouldn’t be able to reproduce.

The federal government filed a lawsuit to limit the amount of water that the Cappaerts could pump. The Cappaerts and Nevada argued that surface water and groundwater should be treated differently. But in a landmark ruling in 1976, the U.S. Supreme Court declared that “groundwater and surface water are physically interrelated as integral parts of the hydrologic cycle.”

The ruling has huge implications for agriculture because groundwater irrigators can now be held responsible for damages they may be causing miles away from their wells. Understandably, many farmers have resisted the notion that groundwater and surface water are connected.

But scientists have shown that too much pumping in a river basin can dry up the river. In Arizona, new wells drilled to supply the burgeoning population of Tucson drained the Santa Cruz River and killed the riverside habitat for wildlife.

In other areas, scientists have introduced radioactive isotopes into streams and tracked them where they came back up out of nearby groundwater wells.

Here’s what happens in the interaction between groundwater and surface water. Most stream beds are not made of impervious rock. The bottom of a stream is porous; water flows in and out, albeit at a much slower rate than the flow of the water in the stream itself. If the surrounding water table is above the level of the stream, the stream is recharged with groundwater and the stream is a “gaining stream.” John Turnbull says that high rainfall around the York, Nebraska, area is recharging the aquifer here. But when an irrigation well begins to pull water from the aquifer, a “cone of depression” forms as water slowly moves toward the well. Slowly, water from the stream moves toward the well, reducing the stream flow. The stream becomes a “losing stream.”

As Arizona Professor Robert Glennon puts it in Water Follies, “Groundwater and surface water are not separate categories of water any more than liquid water and ice are truly separate. The designations “groundwater” and “surface water” merely describe the physical location of the water in the hydrologic cycle.”

Not every state legally recognizes the connection between surface and groundwater.

Oklahoma, for example, flatly refuses to acknowledge any connection. In 2000, the Oklahoma Supreme Court declared, “Where the groundwater surfaces as a spring and forms a stream, it is at that point that the stream water statutes apply.”
Some states, like Idaho and Wyoming, manage surface and groundwater separately in the law, but in practice review water permit applications to determine effects on all water users.
Finally, states like California, Vermont, Utah, and – after the Cappeart decision – Nevada manage all water under a single water code. This is known as a conjunctive management approach. Some states, like New Mexico and Texas, will use a conjunctive approach for parts of the state and other laws for other parts.

The connection between groundwater and surface water is important for farmers because groundwater irrigators may be required to limit their pumping if it affects streams and rivers. That’s what is happening in the Republican River Valley in south central Nebraska. Under a compact between Nebraska and Kansas, it’s been determined that too many
groundwater wells in Nebraska – along with years of low rainfall – are drying up the Republican River and keeping Kansas from getting the water they are supposed to receive. Farmers in Nebraska are being told to reduce their water use, and in some cases may be paid to stop irrigating.

The Natural Resouce District that John Turnbull (left) manages has been involved in monitoring and, some years, limiting the irrigation use of groundwater in the area around York, Nebraska. But, John says that studies the NRD has done indicate that rainfall at the surface will recharge the aquifer underground. “People look at the maps of the styate that show the dots of irrigation wells, and they’re dense in this area,” John says. “And some people draw the conclusion because of all these wells there has to be a problem. Not necessarily… The groundwater level is tied to weather cycles.”