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. ...~.. . . ': JJ:D ~ 11 9 Questien: Will the C1esed Basin Preject turn San Luis Valley into. a dust bewl? Answer: No., the eperatien ef the Clesed Basin Preject will net turn the Valley into. a dust bewl. The fears which many peeple have expressed en this subject are based en mis- understanding. This misunderstanding fecuses en two. efficial statements abeut the preject. These efficial statements are: (1) "the Preject will salvage water now being lost to evapotranspiration ....., II and (2) "decreased plant viger may result (frem the eperatien ef the preject) in seme areas . II Some people have interpreted these statements to mean that operation ef the preject will result in the less ef existing vegetatien frem a vast part ef the valley. That is net what the statements say, and it is net reasenable to. believe this will happen. In the C1esed Basin sump area, the water table is generally 2 to. 6 feet belew the surface. A large amount of water evaporates from the project area every year. Preject facilities are designed to. salvage seIDe (net all) ef this evape- . rated water by lewering the water table in the Closed Basin sump area (enly within the preject beandary). A 1ewer water table will reduce the ameunt ef water transferred from the soil surface and from some of the vegetation to the atmesphere. Water is transferred to. the atmesphere frem leaves ef grewing plants (trans- piratien) and frem the seil surface (evaperatien) by a precess called evape- transpiratien, Plants in the San Luis Valley and the area ef the Clesed Basin (net including wetlands) are well adapted to. lew rainfall and meisture levels; hewever, they can and de use large ameunts ef water when it is available, The efficiency with which a plant uses seil meisture eften decreases with tee much available water. A peint can eften be reached where high meisture levels reduce plant grewth and survival. Where there are always very high water tables, the rate ef plant grewth will likely be less than if the water table and available water were lewer. Lewering high water tables within preject beundaries will net autematical1y result in the death ef all existing vegetatien. Seme plants will be adversely affected by lewering water tables. Others will be helped and increased plant grewth will eccur. Evaperatien ef seil meisture can be very high when water levels are near er at the seil surface. The evaperatien rate frem a wet seil surface generally exceeds that transpired by plants under the same climate cenditiens. Reducing water levels will decrease teta1 water lest frem the seil surface and will eften maintain greater plant grewth rates. Beth upland and wetland vegetatien in the San Luis Valley and the Clesed Basin have been studied fer many years. A 3-year grewth study was cenducted by the Bureau ef Rec1amatien en basically upland vegetatien. The study area was lecated where the water table was 1ewered by a pi1et salvage well. The study has shewn that shrubs right areund preject salvage wells will be adversely affected. Mest ef the shrubs within several hundred feet ef the well will be smaller in size and fewer in number after several years of project operation. Yeunger shrubs will mest likely survive even near the wells. These shrubs have the ability to. fellew the water table dewn as they centinue to. utilize surface precipitatien. Older shrubs de net respend to. rainfall as well. The reactien ef saltgrass and wiregrass to. a lewering mere cemplicated. Where the water table is mere than depend'en direct rain and snewfall fer annual grewth. water table is a little 5 feet dewn, mest grasses In these areas, preject