OCR Text |
Show 2 GROUND WATER IN THE JORDAN VALLEY, UTAH part of the area of artesian flow is derived chiefly from supplies that contain only small amounts of chloride-- namely, seepage from the streams that head in the Wasatch Mountains and rain and snow that fall upon the Provo and Bonneville benches and penetrate downward through the permeable materials that underlie these benches., ; The streams entering the Jordan Valley lose water over portions of their channels below the mouths of their canyohs^ where" they cross the Provo and Bonneville benches. However, the length of channel from which loss occurs is relatively short, as was shown by tests of seepage loss made on some of the streams. The principal area on which direct penetration of rain and snow water takes place is that occupied by the Provo and Bonneville benches. These benches are in most places sandy and permeable and hence are favorable for rapid penetration of the precipitation upon them. The nearly complete absence of drainage channels on the benches is indicative of rapid penetration of the precipitation with no great amount of run- off. The greatest stream losses from Mill Creek and Cottonwood Creek occur in the sections where these streams cross or cut through the Provo and Bonneville benches. On the mountainsides above the benches, between the canyons of the principal streams, are facet- shaped areas which drain onto the benches and not into the principal streams. The small drainage systems on these facets are well developed, indicating considerable run- off. The small streams that discharge onto the benches have built small alluvial cones which, together with the material making up the benches, are favorable for absorbing and transmitting the storm waters that are occasionally poured upon them. A considerable amount of water is contributed to the ground- water reservoir by seepage from irrigation canals and ditches and from the water applied to the soil in irrigation. Recharge from this source is apparent from the facts that the water levels in numerous wells rise when the canals are filled in the spring and drop when the flow through the canals ceases in the fall, and that a considerable net rise has occurred in many wells which were dug or drilled before much water was carried by canals from Utah Lake. The area in which this effect has been most notable is in the southern part of the valley, where some canals run at higher levels than most of the existing wells. It is doubtful, however, whether much of the ground water derived from irrigation supplies reaches the part of the ground- water reservoir that is drawn upon by the artesian wells in the most heavily developed area in the east- central part of the valley. Discharge of ground water occurs in the Jordan Valley through the flow of springs, evaporation from the soil and transpiration from plants in the shallow- water areas, and withdrawals from flowing and nonflowing wells. A large part of the discharge occurs through the several thousand flowing wells that have been drilled in the valley, many of which are allowed to flow continuously. There are numerous springs in the Jordan Valley. East of the Jordan River the upper limit of the area of springs is below the edge of the Provo bench and may be indicative of an overflow from the ground- water reservoir. Much of the water discharged by the springs at altitudes lower than those of the main irrigation canals may be supplied by seepage from the canals and irrigated lands. Considerable areas of land adjacent to the Jordan River are wet and swampy because of spring discharge. Several springs emerge directly from the beds of the streams entering the valley from the east, and it is possible that springs occur in the bed of the Jordan River. There is also some evidence that there are springs in the bed of Great Salt Lake. The water emerging along the upper line of springs, which lie below the Provo bench, may represent overflow from the main ground- water reservoir, or it may be the drainage from a water table perched |