Lake Mead National Recreation Area is one of the most heavily-visited units in the National Park System, and its two lakes are a magnet for recreationists. Falling water levels are requiring some changes that will affect visitors to the area, but the current drought isn't the worst to impact the lake—yet.

Water levels at Lake Mead continue to drop due to the decade-long drought, and two marinas at Lake Mead will be closed temporarily to allow relocation of facilities. The NPS will keep launch ramps at these locations open with temporary extensions.

At Echo Bay, on the Nevada side of the lake, the Marina, fuel dock and marina store will be closed from April 23 through May 5. During those dates, small boat and houseboat rental will be by reservation only (no walk-ins), access to the marina will be by shuttle boat only and no overnight occupancy in the marina will be permitted. All land based services at Echo Bay (RV park, motel, restaurant, store, and fuel) will remain open.

Dates for a similar temporary closure at Temple Bar, on the lake's Arizona shore, are still being determined, but that work is likely to begin soon. You can get an update on current boat ramp and marina conditions on the park website. That site also has a variety of maps to help you plan your visit to the park—and to avoid areas where closures are in effect.

By July, the lake level is expected to be about 14 feet below last year’s lowest point, according to Bureau of Reclamation projections.

Andrew Muñoz, spokesman for Lake Mead National Recreation Area notes,

The major impact on our visitor's summer will be at the launch ramps. However, we have contingency plans in place for temporary extensions using metal pipe mats. Funding from entrance fees and the Southern Nevada Public Lands Management Act will be used to construct permanent ramp extensions.

The lower water levels have implications beyond relocation and use of the marinas. The park staff reminds visitors that boaters should be cautious as new navigational obstructions and reefs emerge. An area that was open water a year ago may now include hazards above—or just below—the surface.

The NPS also recommends that visitors who plan to stroll on the beach wear foot protection. Quagga mussels that previously lived underwater are now exposed along the shore, and their shells are sharp and can cut bare feet.

Falling water levels in the lake create a host of problems that extend far beyond the park.

Lake Mead stores Colorado River water for delivery to farms, homes and businesses in southern Nevada, Arizona, southern California and northern Mexico. About 96 percent of the water in Lake Mead is from melted snow that fell in Colorado, Utah, New Mexico and Wyoming.

The water level in Lake Mead is lower than it has been in over 40 years. The water is going down because the Colorado River runoff over the last decade starting in 1998 has been far below normal.

For some perspective, a NASA website has some interesting aerial photos of Lake Mead, including one that allows you to quickly compare the lake levels in 2000 and 2003.

According to Bureau of Reclamation data, the elevation at Lake Mead early this week will be about 1102 feet, and is predicted to be about 1092 feet at the end of 2009. Things have been worse: in December 1964 it was 1088.14 feet above sea level, and in March 1956 the average monthly level was 1083.57. Lake Mead storage is currently about 46 percent of capacity.

Statistical buffs can find the average monthly level for Lake Mead since 1935 on a Bureau of Reclamation website.

Levels in the big lake have seen some dramatic fluctuations during the past 70 years, and those who rely on the impoundment for their water are counting on history repeating itself with another swing back to a wet cycle. There's plenty of debate among both experts and pundits about when that might happen.

There's a lot more at stake than just the location of the marinas.