A proposal to create a new fresh-water lake by diking off part of the Great Salt Lake is an old idea that has drawn enthusiastic backing from some quarters in recent months. It deserves serious study. Certainly there are plenty of questions that need to be answered.

A measure now before the Utah Legislature, HB208, with some pending amendments, would establish the Great Salt Lake Development Authority, give it limited taxing powers, and provide $250,000 to do basic studies on the proposal.The body of water, to be known as Lake Wasatch, could be developed east of Antelope Island by building about 11 miles of dikes between Promentory Peninsula to Fremont Island to Antelope Island to I-80.

Such a lake would be fed by the Bear, Weber, Ogden, and Jordan Rivers plus 18 smaller streams - fresh water than is now swallowed up in the salty brine of the Great Salt Lake.

Capturing that water would create a lake of four-million acre feet, spread out over an area two and a half times larger than Lake Powell, all within a half-hour drive of the heavily-populated areas of the Wasatch Front.

The dikes, plus the West Desert pumps now operating west of the Great Salt Lake, would enable the lake level to be controlled and offer a stable shoreline - necessary for any commercial development.

Estimated costs are only $80-$90 million. The low figures are due to diking techniques that may cost only a third of conventional dikes.

The Great Salt Lake Development Authority would consist of representatives of the four counties surrounding the lake - Salt Lake, Davis, Weber, and Box Elder. They would have the power to issue general obligation bonds to be paid by taxes levied in those four counties.

Tax rates would be minimal - an estimated $15 per household per year - but could be issued only after voters in the four counties approve the bonds in an election. If Lake Wasatch worked out as planned, the tax bite would be even less because commercial development along the shore would take over much of the burden.

While all of this sounds great, there are serious questions about Lake Wasatch that must be resolved before the project can be given a go-ahead:

What would be the water quality of Lake Wasatch? How long would it take for the water quality to reach a reasonable level? How would fresh water affect the sludge now lying on the bottom of the lake? How serious would resulting algae blooms be? Where would the lake level be set? What would be done with treated sewage now being dumped into the eastern portion of the lake? How would Lake Wasatch affect nearby wetlands and bird refuges? Would the dikes be able to withstand the severe storms on the lake? What makes backers think significant commercial development would take place, given the fact that Willard Bay or Utah Lake shorelines have not experienced such growth? What environmental impacts would there be? What would happen in case of a severe drought? Are there better ways to use the fresh water now going into Great Salt Lake?

These and other questions must be satisfactorily answered before any attempt is made to create Lake Wasatch. The Great Salt Lake Development Authority ought to be established to provide leadership as well as answers. Then the fate of the project will be where it belongs - in the hands of the voters.