March 30, 2012
As Los Angeles as the surrounding areas have continued to develop, access clean drinking water has consistently been a vital factor to sustaining this growth. The reading discussed the channelization and water management factors regarding the Los Angeles River. However, in order to meet the needs of Los Angeles residents many adjacent rivers have required similar control methods. When the San Gabriel flooded in the 1900’s, changing course and dividing into separate rivers, the damage was severe. Since then, the San Gabriel has been dammed multiple times, reducing flood danger and has had channels established along the banks of the San Gabriel and the Rio Hondo. These rivers, essentially the old and new forks of the San Gabriel, have year round flow due to these water control methods which has significant implications for the residents of the Los Angeles Basin.
Although the rivers are now considered in different watersheds, they are both funneled through the Whittier Narrows. Therefore, the Whittier Narrows Dam has become a vastly important structure in flood control and water resources since its construction in the 1950’s.
In conjunction with 4 other dams the San Gabriel River’s danger to residents has been reduced and enhanced providing for recreation and drinking water. The Whittier Narrows Dam itself has about a capacity of 67 k acre ft however the nearby spreading grounds make the area much more effective at storing water than most other dams. By releasing water from the Dam into the spreading grounds the LA county Department of Public Works estimates that 150 k acre ft of water are recharged into the ground supply through the use of these dams.
The spreading grounds are similar in operation to the facilities described in Chapter 3 near Burbank that recharge water in the Verdugo Wash. The water passes through the a treatment facility and then enters the spreading grounds (as pictured above) which have also become an area that supports a wide range of recreational activities. While flood control measures have changed the ecology of the region they were necessary for population growth. It would seem that dams that focus on replenishing groundwater resources should be a focus as demand continues to increase.
The Sepulveda Flood Control Basin and Dam are another example in taming the Los Angeles River.. In 1938, the Los Angeles River flooded farms and homes, killing 144 people and causing about $40 million in damage ($360 million in 1994 dollars). As a consequence of the historic 1938 flood, the public demanded that the river be controlled. The Army Corps of Engineers began channelizing the river in 1938, completing work in 1960. Located near the intersection of the 101 and 405 freeways, the Sepulveda Dam was completed in 1941 to further protect San Fernando Valley residents from floods.
During winters when waters stream down from high elevations, the reservoir can hold up to 17,000-acre-feet of water. The dam and basin control the heavy winter flow rates, preventing flooding of the river downstream along the Los Angeles River, also allowing the trapped runoff to seep back into the water table without causing further damage. Recently, in the 1980 flood, water reached about twenty from the top of the dam, filling the dam to about two-thirds of its capacity.
Although the central function of the flood basin is the control of floods, the basin has enjoyed a new role. Beginning in the 1960s, the Sepulveda Dam and its surrounding area has played host to many recreational activities. The area includes many golf courses, sports centers, and parks. The most interesting feature of the park being Lake Balboa, a 27-acre lake filled with reclaimed water. Visitors participate in activities such as fishing, boating, jogging, and bicycling along a paved bike path. The area also includes aJapaneseGarden at the Donald C. Tillman Water Reclamation Plant, where visitors can see evidence of the peaceful and beautiful uses of water.
The reclaimed water enters the Los Angeles River in the Sepulveda Basin. As much as 75 million gallons of water is released daily from the reclamation plant into the basin, adding to the Los Angeles River’s modern day year-round supply. While this water is not suitable for drinking, it has been treated enough to not pose a health hazard. This treatment is vital for the wildlife that resides in the basin today. The Sepulveda Basin Wildlife Reserve gives visitors an idea of what Southern California looked like before agriculture and industrialization changed the valley. Visitors might find cottonwoods and sycamores lining the valley, along with birds such as herons, egrets and ducks. Small birds like the woodpecker and oriole also make homes in the Reserve.
The Whittier Narrows Dam and the Sepulveda Dam are two of the 19 dams in Los Angeles, helping to prevent floods and also recharging groundwater from rainfall and runoff. As the Los Angeles population grows, these two projects work towards replenishing the dwindling water supply and protecting residents from natural disaster. Whittier Narrows and the Sepulveda Basin have proven a great opportunity to educate the public and promote efficient water use, serving as a recreational area in addition to their roles as a flood-control basins. The flood control measures at both sites sprouted from residential problems with population growth in an area where floods were likely. Their focus on flood control, groundwater recharge, and recreation has without doubt added to their success.
This post was written by Daniel Kasang ’12 and Christopher Miranda ’12, who are each pursuing a B.S. in Environmental Studies.