1.2: Water Management Concepts
Let's engage in a little thought experiment.
If a zombie apocalypse happened right now and you ran for the hills, you would have to find water to survive. How would you go about doing this? In this section, you’ll identify sources of water supply. This section is critical to an understanding of water management, both personally as well as regionally and statewide.
Learning Objectives
- After reading this section, you should be able to:
- Describe various sources of surface and groundwater supply
- Give examples of water storage
- Evaluate a situation in terms of conjunctive use
Now back to the zombie apocalypse. If you had to find water, you would probably:
- Try to find a stream or lake
- Start digging a well
Notice that you didn’t start with the ocean. This is important because most of us intuitively understand the amount of energy it takes to make ocean water drinkable. Although most of the water on earth is in the oceans, bays, and seas, it’s not drinkable without expensive treatment. Who would have time for that level of treatment in the zombie apocalypse? And you also didn’t start with the ice caps (too far and too many zombies in the way). What you have intuitively chosen is the right solution—surface water and groundwater. And your strategy reveals another challenge for water managers—most of the water on earth is not accessible or easily potable (drinkable).
Most of the water on earth is in the ocean (97%). For the 3% that remains as freshwater, most of it is trapped in glaciers and ice caps (68.7%). That leaves only groundwater and surface water making up less than 1% of the water on earth. You can see why people refer to water as precious! In fact, 20% of all freshwater on earth is in one enormous lake in Russia, Lake Baikal, which is inaccessible to most of us on earth.
Surface water can be broken into different types, but it is easiest to think of surface water as either bodies of water and flowing water. Surface water can occur as a lake or pond, both bodies of water at low places in the land where water has accumulated. Most lakes have both inflow and outflow. Some lakes lack inflow and/or outflow and they become salty over time (e.g., Great Salt Lake, Dead Sea, Salton Sea). A reservoir is a lake that is manmade by making a dam across a river.
Surface water can be flowing water, such as a creek, stream, or river. It can also be water stored in a lake or reservoir. People tend to use the terms creek, stream or river interchangeably. Rivers (or streams or creeks) form when water moves from higher ground to lower ground. You’ll remember that in the water cycle, gravity is a driving force—all water flows downhill. When water falls from the sky as rain in the water cycle, it may infiltrate into the ground, but it also may run off and form creeks and streams. Eventually, creeks, streams and rivers flow to the ocean.
As a source of water, surface water has both benefits and drawbacks.
|
Benefits of Surface Water |
Drawbacks of Surface Water |
|---|---|
|
Easy to access |
Water is lost to evaporation |
|
Lakes and reservoirs can provide flood control in addition to a water supply |
Lakes and reservoirs may experience a build-up of sediment, especially after fires |
|
Distribution requires a network of pipes and/or canals |
Well, nothing is perfect in the study of water supply. If surface water isn’t the perfect supply, perhaps groundwater is better. In the diagram below, you can see both surface water and groundwater. The water table is the line at which soil becomes saturated with water. The soil above the water table is unsaturated and the water below the water table is saturated. Groundwater is stored in aquifers, which are areas underground of soil or rock that can hold and transmit water beneath the water table.
Misconception Alert!
Frequently, people will describe an aquifer as an underground swimming pool. While this does illustrate the idea that water is stored underground, it is really misleading. A swimming pool contains water entirely. An aquifer is mostly sediment or rock with water in the pores between grains of rock or sediment.
Sediment and rock vary in terms of how much water it can store. The ability for rock to transmit media is often referred to as permeability. Sometimes gravel has large pores and rock has large connected fractures that enable water to move through them. Other times, the pores in gravel and the fractures in rock are impermeable.
In order to get water from the aquifer to the surface, you need either the water to come up from the ground naturally because of pressure in the layers confining the aquifer or you need to drill a well, which is much more common. In the diagram below, you can see the difference between a deep well and a shallow well. When the water table is at a normal level, both the shallow and deep well can produce water. However, when it is a drought, only the deep well can reach below the water table. The shallow well would end up being dry.
Groundwater as a water supply also has benefits and drawbacks that communities consider when they build their water supply portfolios.
|
Groundwater Benefits |
Groundwater Drawbacks |
|---|---|
|
Difficult to pollute |
Difficult to clean up |
|
Useful in times of drought when surface supplies are low |
Replenishment is slow |
|
Generally, cheaper |
Hard to manage as levels dwindle |
|
No need for an expensive network of pipes and canals to transport long distances |
Visual inspection is difficult |
Some communities use both surface water and groundwater as a supply. In years of heavy snowfall and deep snowpack, there may be abundant surface water available. In this case, surface water would be used for water supply while groundwater supplies could be allowed to replenish naturally through the infiltration of rainfall. In addition, surface water could be stored in groundwater basins to aid in replenishment. In the reverse situation, in years of light rainfall and little snowpack, groundwater would be relied on as a primary source because surface water was not a sufficient supply. The practice of alternating water supplies to meet the needs in a community is called conjunctive use.
Both surface water and groundwater can provide adequate yearly sources of water, but it is best to have water stored for use in dry years or for emergencies. Water can be stored above ground in reservoirs and below ground in banks. Storing water in reservoirs makes it readily accessible in times of drought or emergency, such as fires or if part of a distribution system goes out of service. Storing water in the ground can be done in water banks, such as the banks in Kern County.
In these banks, water is injected or infiltrates directly into an aquifer. It can be retrieved later for a fee during times when groundwater and surface water are not sufficient. Many water districts find that storing water in various water banks can diversify their water supply portfolio, giving them more flexibility in providing water in dry years.
How can you make your water supply more reliable? Think of the last drought. You probably noticed lower levels in surface water at lakes and reservoirs and even in streams. In the photo comparison, you can see the difference in just over a month's time in 2014 in the visible shoreline. In this example, more water has been taken from the reservoir to treatment facilities during the late spring in 2014 with a very visible effect on the appearance of the lake!
In California, typically, it is only through a combination of water supplies that you can have a reliable water supply. The best scenario is that you have a water supply that consists of multiple sources of groundwater and surface water. That way, when one source is dry or less reliable due to a drought or unusable due to a water quality issue, you have a backup. The ultimate scenario for water supply reliability also includes a supply of water in storage.
In Santa Clarita, there are multiple sources of water supply for the water retail companies. Sources of supply include relatively shallow groundwater wells into the alluvium, clay, silt, and gravel, as well as deeper groundwater wells into the Saugus formation. While the shallower alluvial wells provide a source of relatively inexpensive supply, they also tend to be more sensitive to droughts. Imported water from the State Water Project makes up roughly 50% of the water supply in a normal year though the amount in this supply relies entirely on the snowpack in the Sierra Nevada Mountains.
During the last drought in Santa Clarita when water deliveries from the State Water Project were at a minimum, groundwater pumping was increased above normal year levels. When deliveries from the State Water Project returned to pre-drought levels in 2017, groundwater wells were pumped less in order to let the well levels recover. This is a classic example of conjunctive use that brings together what you've learned about groundwater and surface water because of the alternation of supplies in order to achieve greater reliability.
Now that you understand the concepts used to manage groundwater and surface water, let's take a look at water rights in California.
Try It!
- Identify at least three potential sources of water that you could use during the zombie apocalypse.
- Describe the drawbacks of surface water and groundwater.
- Many communities in California rely on groundwater and surface water. Explain how conjunctive use might apply.
Key Terms
Alluvium—Clay, silt, or gravel left from old rivers
Aquifers—Areas underground of soil or rock that can hold and transmit water
Conjunctive use—Use of alternating water supplies to meet the water demands
Permeability—The ability to transmit water
Potable—Drinkable water
Reservoir—A lake that is manmade by making a dam across a river
Surface water—Flowing water, such as a creek, stream, or river; also still river stored in a lake or reservoir
Water table—The line at which soil becomes saturated with water