Geology topics

Research about Mojave River

Source-linked reports with geographic coverage including Mojave River.

3 recordsLinked to original sources

USGS1999

Health of native riparian vegetation and its relation to hydrologic conditions along the Mojave River, southern California

The health of native riparian vegetation and its relation to hydrologic conditions were studied along the Mojave River mainly during the growing seasons of 1997 and 1998. The study concentrated on cottonwood-willow woodlands (predominantly Populus fremontii and Salix gooddingii ) and mesquite bosques (predominantly Prosopis glandulosa ). Tree-growth characteristics were measured at 16 cottonwood-willow woodland sites and at 3 mesquite bosque sites. Density of live and dead trees, tree diameter and height, canopy density, live-crown volume, leaf-water potential, leaf-area index, mortality, and reproduction were measured or noted at each site. The sites included healthy and reproducing woodlands and bosques, stressed woodlands and bosques with no reproduction, and woodlands and bosques with high mortality. Tree roots were studied at seven sites to determine the vertical distribution of the root system and their relation to the water table at healthy, stressed, and high-mortality cottonwood-willow woodlands. In the six trenches that were dug for this study in May 1997, no cottonwood roots were observed that reached the water table. The root systems of healthy trees typically ended 1 to 2 feet above the water table. At sites with high mortality, the main root mass was commonly 7 to 8 feet above the water table. Water-table depth was monitored at each of the study sites. In addition, volumetric soil moisture and soil-water potential were monitored at varying depths at three cottonwood-willow woodland study sites and at two mesquite bosque sites. Ground, soil, river, lake, and plant (xylem sap) water were analyzed for concentrations of stable hydrogen and oxygen isotopes to determine the source of water used by the trees. On the basis of the root-distribution, soil- and leaf-water potential, and isotope data, it was concluded that cottonwood, willow, and mesquite trees mainly rely on ground water for their perennial sustained supply of water. The trees mainly utilize ground water that has moved upward from the water table into the capillary fringe and into unsaturated soil nearer to land surface. Most precipitation (average is 4 to 6 inches per year) is lost by evaporation and by transpiration of shallow-rooted xeric plants, and very little reaches the root zone of trees along the Mojave River. Water-table depth had no strong correlation to many individual tree-growth characteristics, such as density, diameter, height, and live-crown volume. However, leaf-area index (corrected for stem area) of both healthy and stressed cottonwood-willow woodlands had a highly significant statistical relation to water-table depth, and a curvilinear regression model was defined. As in cottonwood-willow woodlands, leaf-area index of mesquite bosques also decreased with increased water-table depth. However, because of the small number of sites, no significant statistical relation could be defined for mesquite bosques. Because it can be accurately measured repeatedly at the same locations, leaf-area index (corrected for stem area) is recommended as the primary growth characteristic that should be monitored. Future vegetation changes along the Mojave River can be quantified using the sites established for this study. Mortality was as high as 39 percent in healthy cottonwood-willow woodlands, but mortality of 50 to 100 percent was common where water-table depth was greater than about 7 feet or in areas where permanent water-table declines greater than about 5 feet had occurred. At a healthy mesquite bosque where the water-table depth ranged from about 8 to 11 feet, mortality was about 20 percent. Where the water table had been lowered an additional 10 to 25 feet by pumping, mortality of the mesquite was extremely high (80 to 99 percent). On the basis of observations of plant reproduction, it was concluded that established cottonwood-willow woodlands probably will reproduce, mainly by root sprouting of mature trees, if the water-table depth during spring and early summer is less than about 5 feet and if there is sufficient sunlight. Likewise, reproduction in established mesquite bosques will probably occur by root sprouting if the water-table depth during spring and early summer is less than about 8 feet. Germination of cottonwood and willow seeds is common during spring in dry channels following winter stormflows in the Mojave River. However, most of the seedlings die before their roots reach a perennial water supply near the water table, and established stands of trees resulting from seed germination are rare.

California↗

USGS1996

Ground-water and surface-water relations along the Mojave River, southern California

The Mojave River and the associated floodplain aquifer are important water supplies in the Mojave Desert of Southern California. The river and aquifer, in many areas, are in excellent hydraulic connection, and when flow conditions change in one, the other almost always is affected. To better understand these relations, records of gaging stations were analyzed to determine the frequency and duration of historical streamflow. Annual ground-water recharge from the river during water years 1931-94 was estimated from an accounting of all streamflow accretions and losses. Annual recharge ranged from about 24,000 to 460,000 acre-feet and averaged about 96,000 acre-feet. Channel-geometry regression techniques were used to estimate runoff of ungaged ephemeral streams that are tributary to the river. Water-table and gravity changes were used to estimate specific yield of the aquifer and changes in ground-water storage following storm runoff during the winters of 1992-94. In addition, streamflow hydrographs were analyzed to estimate both ground-water discharge to the river (base flow) and historical streamflow depletion caused by ground-water pumping and evapotranspiration. Ground-water pumpage from the flood-plain aquifer was about 120,000 acre-feet during water year 1994. Annual evapotranspiration along the river probably ranges from about 10,000 to 30,000 acre-feet. Factors controlling the exchange of water are identified in this report on the basis of the historical response of the river-aquifer system to stress (stormflows and pumping). Also identified are reaches of the river that are hydraulically suitable for artificial recharge.

California↗

USGS1974

Hydrologic analysis of the Mojave River, California, using a mathematical model

The channel of the Mojave Rive'r in California is normally dry and is highly permeable over much of its length, and large quantities of water from natural floodflows in the channel infiltrate through the channel bed to the underlying ground-water body. From 1930 to 1972 only 18 floods at The Forks produced flow at Barstow, 55 miles (88 kilometres) downstream from The Forks. Peak discharges at Barstow from these floods ranged from 180 cubic feet per second (5 cubic metres per second) in 1967 to 64,300 cubic feet per second (1,820 cubic metres per second) in 1938. Total stream infiltration, primarily as ground-water recharge, ranged from 3,600 acre-feet (4.40 cubic hectometres) in 1935 to 50,400 acre-feet (62.1 cubic hectometres) in 1969 between The Forks and Victorville and from about 7,000 acre-feet (8.61 cubic hectometres) in 1935 to 128,000 acre-feet (158 cubic hectometres) in 1969 between Victorville and Barstow. The Mojave Water Agency is considering the use of the channel of the river to convey water imported from northern California through Silverwood Reservoir (5 miles or 8 kilometres upstream from The Forks) downstream to the Barstow area. The imported water would be used to replenish aquifers underlying the Barstow area. A mathematical model was developed that simulates the advance of discharge down the initially dry channel of the Mojave River, and the model was used to evaluate the potential of the channel to move imported water downstream to Barstow. Results of simulation by modeling indicate that the channel of the Mojave River can be used to efficiently convey imported water to Barstow only when the absorption capacity of the channel has been reduced by an antecedent flood. The volume of imported water that can reach Barstow depends on the volume and duration of the antecedent flood, on the volume of imported water released trom Silverwood Reservoir, and on the rate at which imported water is released. A release of 20,000 acre-feet (24.6 cubic hectometres) of imported water may produce at Barstow a maximum volume of imported water of 2,500, 8,000, 11,000, or 15,000 acre-feet (3.08, 9.86, 13.6, or 18.4 cubic hectometres) for a release rate of 500, 750, 1,000, or 2,000 cubic feet per second (14.2, 21.2, 28.3, or 56.8 cubic metres per second). For planning purposes in evaluating some of the hydraulic effects of recharge on the aquifer, a simulation of the aquifer near the Barstow area using an electrical analog model showed that a combination of no pumping and a yearly recharge of 5,000 acre-feet (6.17 cubic hectometres) for 10 years could raise ground-water levels at least 10 feet (3 metres) over an area of about 10 square miles (25 square kilometres). To obtain the water-level changes due to the combined effects of pumping and recharge, the above water-level changes should be superimposed on the separate effects of pumping.

California↗