The echo of Rain

Thousands of cubic feet of water pour through California's aqueducts every second; three years of drought are slowing this quantity to a trickle. The system that delivers water to California's dry southlands may be what holds the state together through drought.

By Holly McKelvey

California is bone dry these days.

Drive through its Central Valley, the rich agricultural breadbasket of the States, and you will see kilometer after kilometer of desiccated, empty fields. The brown is broken by an occasional green oasis of almonds or artichokes fed by drip systems or by the feeble arc of sprinklers, which seem to evaporate under the heat of the day before they touch the ground. But even these patches of production seem gray against the desiccated backdrop of the Valley.

The problem? The state of California has plunged into exceptional drought. Rain is rare, snow in the mountains is effectively absent, and demand for water is high. Four years of drought have slowed the movement of water from the state's wetter north to its drier south to a trickle: zero percent of allocated water was delivered to Californian counties in 2014, and this year may well be the same. In January, governor Jerry Brown officially declared a state emergency.

For a state that is home to 38 million people and relies on an annual $23 billion economy in agriculture, running out of water is not an option. But when water is severely limited, as during drought conditions, overdrawing California's water sources to sate its thirsty southern cities and the Central Valley can be environmentally devastating. The management of California's water becomes a precarious balancing act between keeping the water flowing south to cities and fields, and protecting the state's ecological health.

The water that sustains California is predominantly supplied by just two sources: snowmelt from California's eastern mountain range, the Sierra Nevada; and groundwater. California's water management during wet years thus involves capturing rainfall and snowmelt during the winter and spring, and storing it for distribution during the dry summer and autumn. During dry years, dependence shifts to groundwater.

Wet years herald rainfall throughout California, and a snowpack in the Sierra Nevada. In the spring snowmelt pours down from the mountains, feeding two vast rivers that converge and empty into the Pacific Ocean: the San Joaquin, and the Sacramento. The convergence forms an estuarine wetland at the northern end of the Central Valley, the Sacramento-San Joaquin Delta. This wetland, a fragile buffer between the fresh water of the rivers and the saltwater of the Pacific, is the heart of California's water allocation system.

From the southern end of the Delta, a series of pumps divert thousands of cubic feet of water per second south to Central Valley fields and southern cities via an elaborate series of aqueducts and canals. In an average year, an incredible 2.2 trillion gallons of water are moved south through this formidable system of engineering. The great theme of California's water allocation is this: north to south.

This movement of water from north to south began in the 1800s, when much of California's Sacramento Valley (in the northern Central Valley) was an extensive marshy wetland. Although the soil was rich, it was unusable for agriculture, and early landowners drained it via canals, embankments and pumps. By the 1930s, much of the former wetland was being farmed; and floods, caused by sedimentation from mining during the gold rush of 1849, were a frequent problem. It seemed logical, therefore, to move water away from the north, where it was causing so many problems, to dry agricultural fields and urban centers in the south. A bulletin from the Department of Water Resources from 1968 described "barren sagebrush lands... being transformed into irrigated fields" by the new aqueducts of the State Water Project. "Nature has not provided the right amount of water in the right places at the right times," reads the report. "The solution to California's maldistribution of water resources has been one of conserving the sporadic stream runoff in surface storage reservoirs and transporting the regulated supplies to areas of use." Whereas winter was the only reliable growing season in the past, now farmers could grow year round. A field that lay fallow in summer was a field wasted.

The legacy of this water redistribution is twofold: first, extensive infrastructure now exists for managing water in the state of California. Second, due to this infrastructure, cities and agriculture were able to thrive in areas that would otherwise be too dry to support such thirsty uses, creating a dependence on water delivery that has only grown. Los Angeles, the sprawling metropolis of nearly 4 million residents in California's dry south, uses approximately 196 billion gallons of water per year. But demands from this and other city landscapes make up just 20% of the diverted water in California. A further 80% goes to California's economic mainstay: agriculture.

Such a huge dependence on water redistribution demands that water keep flowing year-round. Cities do not slumber in summer, after all; and the California's agricultural production continues from January to December. Yet water is a seasonal commodity in California: even in a wet year, it does not flow year-round. Traditionally, dams and reservoirs store water from the wet winter and spring in order to supply the dry summer and fall. But for the past three years, the winters have been relentlessly dry. This winter (2014-15), is currently seeing only 8% of the average snowpack in the Sierra Nevada. As a result, the dams and reservoirs are not being refilled: water storage for the dry summer months is low.

Empty reservoirs means less water sent to California's dry south. What happens to water allocation, then, without the winter rains and snowmelt?

For a start, the huge pumps that divert water south from the Delta slow down. With less water flowing into the estuary from upstream, the pumps risk sucking saltwater into the wetlands from the ocean. This would pollute drinking water and impact the rich, fertile farmland along the Delta; and it would threaten the delicate estuarine ecosystem. To prevent such an environmental catastrophe, the amount of water pumped south during drought years drops dramatically.

Protection of the Delta's biodiversity has limited water diversion even in less dry years: one of the largest estuaries in North America, the Delta is home to a spate of threatened species, including salmon, trout, and the delta smelt. The latter (Hypomesus transpacificus), an endangered and sensitive endemic long considered the proverbial canary in the mineshaft of the Delta, has been a polarizing figure in the last several years.

Many conservationists have argued that the decreasing population of the delta smelt means that too much water has been drawn from the Delta; in 2007 water pumping from the Delta was limited to protect the smelt, and in 2010 the fish was listed as endangered, affording it further protection. Citing the Endangered Species Act of 1995, the United States Congress determined that the smelt offered "aesthetic, ecological, educational, historical, recreational, and scientific value to the Nation and its people." But Central Valley farmers have condemned the protection of the smelt, arguing that preserving the fish's ecosystem by sending less water south is harming California's agricultural sector.

The second impact of decreased snowmelt is an increased dependence on groundwater, California's second main water source. This is where things become risky. Snowmelt is a renewable water source; groundwater, if over-depleted, is not. Bodies of groundwater, called aquifers, consist of a layer of porous rock that contains water, often millennia old. They are recharged when precipitation and surface water filter down through the soil. But when water is sucked out of these ancient underground water sources faster than they can recharge naturally, compaction occurs: the space occupied by water closes up, causing land subsidence above, and preventing the possibility of recharge. During normal and wet years, about 38% of the state's water comes from the ground; during the last few years of drought, this has leapt to almost 50%. Most of this is for agriculture.

The repercussions of the overdraft of groundwater are manifold. From a human perspective, it means that domestic wells run dry as the groundwater level falls deeper than the wells reach. From an economic perspective, it means that farmers lose money digging deeper and buying stronger and stronger pumps to bring water up from great depth; and infrastructure such as roads, aqueducts and more can be damaged by the uneven subsidence of the ground. And from an environmental perspective, the implications are long-lasting: compaction prevents further recharge of aquifers, areas that have held water for millennia; the suction of pumps can cause intrusion of deep saline groundwater into aquifers, degrading water quality; and streams and lakes fed by groundwater fall dry, or suffer from these saline intrusions.

Perhaps the biggest threat of the current overdraft is that, during future droughts, California will no longer have groundwater to fall back on when water deliveries from the Delta are reduced.

Despite these threats, California remains one of the few states in the US not to regulate how much water can be pumped from underground. Without water from the Delta and the Southern Sierra Nevada Mountains to supply agricultural fields in the Central Valley, groundwater is currently being drawn up at much faster than it can be recharged. Traditionally, groundwater has been drawn up at a rate of approximately 800 billion gallons per year. Last year almost 5 trillion gallons were drawn up. Groundwater levels have dropped by as much as 40 feet in some parts of the Central Valley. The dependence on groundwater is unfettered.

What, then, are the solutions? What is California doing to balance the needs of its human populations, the economic wealth and millions of jobs provided by agriculture, and the health of its ecosystems?

New legislation to change water use is slowly creeping into place, spurred by necessity. A recent bill passed by the California Senate has required that the state reduce per-capita water use by 20% by 2020. In response, cities are raising water rates, rationing water, and charging fines for water waste in order to minimize water per capita use, as well as recycling water, capturing more storm water, and pursuing desalinization projects in order to increase local water availability. Los Angeles could become completely independent from northern water by 2050, even as its population continues to grow.

To address the threat of overdrawing groundwater, the Sustainable Groundwater Management Act was signed into existence in September 2014; this marks the first step that California has taken to limit groundwater usage. Under the Act, groundwater management will occur at the local level, with the aim of minimizing overdraft and subsidence within the next decades. Through a series of deadlines over the next ten years, counties in California will identify high and medium priority groundwater basins, and meet various conservation criteria outlined by the Act, including limiting the amount of withdrawal, and contributing to aquifer recharge. Critics have suggested that the timelines proposed in the Act are overly generous. The water crisis is now.

Many are concerned by the potential impacts of climate change on California's water supplies, as well. Increased global temperatures will bode increased heat waves, higher night-time temperatures, and longer summers. Under these conditions, the snowpack could continue to dwindle, and the water that is collected will evaporate at faster rates from the surface of reservoirs and aqueducts. Drawing water from the Delta will become more complicated as well: as sea levels rise, salt water will intrude further into the estuary, especially when the pumps pull out fresh water to send south.

These conditions will not necessarily be impossible to navigate, however; many are optimistic that California will be able to minimize its water use sufficiently, and manage its water wisely enough to successfully ride out future droughts. Jay Lund, a Professor in the Department of Civil and Environmental Engineering at UC Davis, notes that the infrastructure in California allows an extraordinary amount of resilience to drought conditions. "Every year California has a worse drought than most of the US has ever seen, just by the nature of its Mediterranean climate," Lund points out, "so our irrigation system and our big water system really give us much more robustness to changes in climate, or any other change that affects the water system, than most other parts of the country."

Longterm drought would have its impacts, certainly; but the great movement of water from north to south is the very tool that will allow California to ride through the drought.

Holly McKelvey is a graduate student in Applied Ecology at the Christian-Albrechts University of Kiel, Germany, working on bio-indicators in stream ecology. She can be reached at mckelvey.holly@gmail.com