California Water Resources: Hydrology, Projects & Climate

Introduction

The California state water system has a plethora of interesting features and dynamics that are complex, and its hydrology continues to evolve. Although there have been massive projects to harness the state's water and deliver it to areas that need it — such as urban or agricultural centers — there have been many consequences to these actions. Water quality is steadily degrading throughout the entire system, and the construction of the infrastructure itself has caused serious environmental problems as well as the loss of natural habitats. In fact, roughly 95% of the state's wetlands have already been lost forever. Furthermore, one of the most alarming factors is that California's water distribution system was built on a precipitation model that is becoming increasingly irrelevant. Climate change is predicted to heavily influence precipitation patterns in the future, and the entire water distribution system may have to be altered to meet these challenges.

Background on California's Hydrologic Cycle

The term hydrology refers to the science that encompasses the occurrence, distribution, movement, and properties of the earth's waters, and their relationship with the environment within each phase of the hydrologic cycle.¹ The hydrologic cycle begins with evaporation, as heat changes liquid water into gas, and ends in condensation, as it cools and returns to the earth. The precipitation becomes runoff and collects in a body of water depending on where it flows. Much of the water will eventually end up in an aquifer, which is an underground storage area for water.

California's statewide average precipitation is approximately 58 centimeters, which equals 200 million acre-feet of water deposited annually; however, this precipitation is not distributed equally across the state. Approximately 75% of the runoff occurs north of Sacramento.² The 78 million acre-feet (maf) that falls on a yearly average is allocated to environmental uses (46%), agricultural uses (46%), and urban use (11%). However, this figure is only an average and can fluctuate considerably from year to year. One of the primary factors that influence these levels is drought, during which rainfall does not meet average levels. Floods, on the other hand, can be caused by excess rainfall that produces more runoff than the land can absorb, creating impromptu rivers and streams that damage both natural and human-made structures. Too little rainfall can result in dry conditions in which wildfires occur. The level of annual precipitation is therefore vital to California's well-being.

California's Hydrologic Regions

The Central Valley contains three hydrologic regions. In the north end of the state, the Sacramento River Region drains the northern half of the Central Valley, which remains a major agricultural area. The Sacramento River carries almost a third of the entire state's runoff and receives most of that runoff from the west slope of the Sierra Nevada Mountain Range. The next region is the San Joaquin River Region, which is bounded by the Coast Ranges and the Sierra Nevada crest and relies heavily on groundwater for agricultural and other uses.

The North Coast Region occupies the northwest corner of the state and receives over 250 centimeters of rain per year, resulting in rivers and streams that collect almost half of the state's total runoff. The Central Coast Region covers nearly 300 million hectares and contains roughly 4% of the state's population; much of this region is rural and agricultural. The final coastal region is the South Coast Region, which is California's most heavily populated area, containing roughly half the state's population yet receiving only about 2% of the state's entire precipitation. Numerous water storage and conveyance projects have been completed to help supply the urban demand in this region.

The three remaining regions are the North Lahontan, the South Lahontan, and the Colorado River Region. Lake Tahoe resides in the North Lahontan Region, and most of the water in this region is used for cattle ranching. The South Lahontan contains Death Valley as well as both the highest and lowest elevation points in the contiguous United States. Although the Colorado River Region is named after the Colorado River, it does not actually receive much direct runoff from it. There is, however, an accidentally created lake called the Salton Sea, which has become an important habitat for birds as most of their natural habitats have been converted for human development. The Salton Sea National Wildlife Refuge (NWR) and the adjacent Imperial Valley contain over 380 individual species of birds and hold the distinction of having the most diverse array of bird species found on any national wildlife refuge in the West (USGS).

Conclusion

The current hydrological cycle in the state of California is one of the most complex in the world and contains many unique features. Humans have greatly altered the natural water system in a variety of ways, which have mostly resulted in negative ecological consequences. However, there have also been some unanticipated benefits, such as the accidental formation of the Salton Sea, which is now the most diverse bird habitat in the West. Yet California will face serious challenges in its ability to control and maintain its water systems. As climate change alters precipitation patterns, much of the existing distribution infrastructure will fail to adapt without significant modification. This challenge, coupled with ongoing water quality degradation, will pose formidable difficulties for all future generations of Californians.

Works Cited

Hyslop, R., and L. Wu, and S. Garver. "California's Water Resources." California Electic: A Topical Geography. Pomona: [University], n.d. Print.

USGS. "Bird Checklists of the United States." 1 February 2013. Northern Prairie Wildlife Research Center. Online. 3 December 2013.