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Water Storage Helps Preserve Instream Flows
Low summer stream flows have emerged as the most significant obstacle to the recovery of listed coho, Chinook and steelhead in the Mattole River watershed. Sanctuary Forest, a southern Humboldt County land trust, established the Mattole Flow Program in 2004 with the goal of restoring healthy in-stream flows for fish and people.
Early in the program hydrologic and water use studies identified that human use is a significant contributor to low flows and is the most controllable factor in restoring in-stream flows. Guided by these insights Sanctuary Forest actively promotes water storage and seasonal forbearance of water withdraws as a cornerstone of the Mattole Flow Program.
To help landowners develop large capacity water storage and benefit fisheries, Sanctuary Forest developed the “Water Storage Guide”. This handy manual is designed to be distributed by water storage retailers with the sale of a tank.
The information and concepts contained in the “Water Storage Guide”, while developed in the Mattole, are largely transferable to any watershed. Below is a summary of the main points of the guide. You can obtain a full version of the guide online at sanctuaryforest.org
Fish Friendly Water Storage
There are four key elements to fishfriendly water storage:
- Calculate your household’s water storage needs for the low-flow season.
- Fill and top your tank(s) outside of the low-flow season.
- Limit pump rates and use fish screens to protect small fish.
- Monitor your weekly water use to meet your water budget.
These guidelines, and other important steps you can take, are explained in the following sections. When we refer to the “low-flow season,” it is important to realize that the calendar is not a perfect guide to when you should stop pumping from your creek or river. The most important guide is the actual level of streamflows at the point where you are pumping.
To get more detailed information about streamflows and recommended no-pump periods outside the Mattole, contact your local watershed group or your nearest Department of Fish and Game office, or check the data on streamflows available through the U.S. Geological Survey.
Calculating Your Water Storage Needs
We recommend that every household store enough water to last for a dry season stretching three months, or 105 days.
- Household water use: 55 gallons per day (gpd) per person
- Garden water use: 18.5 gpd per 100 square feet of garden
- Fire protection water reserve: 2500 gallons
Sample storage calculation for a 3-person household with a 1600 sq ft garden:
- Household water need (Aug 1–Nov 15): 17,325 gallons (105 days x 3 people x 55 gpd)
- Garden water need (Aug 1–Oct 15): 22,496 gallons (based on 76 days x 1600 sq ft x 18.5 gpd per 100 sq ft; this assumes that households will stop irrigating their gardens after October 15, which is recommended)
- Fire protection: 2500 gallons
- Total household storage need: 42,321 gallons (for 3 months)
This figure represents the household’s required storage for the full 3 1/2-month dry season from August 1 through November 15. If you are unable to store enough water for this entire period, make sure at least that you have adequate storage to last through the two lowest-flow months of September and October—that is, at least 60 days’ worth of water.
Fill and Top Your Tanks Outside the Low Flow Season
As a general rule, you should fill your tank no later than May 31 to ensure minimal impacts to flows and optimum water quality. Ideally you should stop pumping entirely from August 1 until November 15.
Avoid overfilling your tank and causing significant water losses. Two recommended methods to ensure against overflow losses are installation of an automatic shut-off valve that turns your pump off when the tank is full, and overflow piping back to the water source.
To protect fish habitat and prevent direct harm to juvenile fish, pumping rates should never exceed 5% of the streamflows of the water source, and in general pump rates should never go above 11 gallons per minute (gpm), which is adequate to fill tanks in an efficient manner.
Installing and Maintaining Fish Screens on Pumps
All pumps need to be equipped with intake screens to prevent damage to small fish. The screen openings must be small enough so that small fish can’t get sucked into the pump. Additionally, the total screened area needs to be large enough so that the suction pressure against the screen is almost non-existent. It is very important to clean pump screens regularly to avoid clogging. When pump screens become partly blocked by debris, the suction pressure on the remaining screen will be higher, potentially injuring juvenile fish.
Monitoring Weekly Water Use
A water budget is an essential way to ensure that your stored water will last through the low-flow season, along with weekly monitoring of your water usage. In its simplest form, a water budget takes your total water storage capacity (excluding fire reserve) and divides it by the number of weeks when you will stop pumping. By measuring your weekly usage you can ensure that you’re staying “within budget” -- and make adjustments if you are not.
The easiest way to measure usage is to install a water meter (cost: about $200) on the outlet of your tank, and record usage on a weekly log. The water used per week is then easily calculated from the log and can be compared with the water allocation to make sure that water use is on budget.
Alternatively, you can manually calculate your weekly water use by taking depth measurements of your tank and using these to figure the change in volume. You can reduce water use by up to fifty percent during the dry season by following these tips:
- Reduce irrigation water by watereffi cient gardening and landscaping techniques: dry farming and droughtresistant plants, drip irrigation, mulching, evening watering, avoiding overwatering.
- Reduce household water use by using efficient fixtures and turning the water off except when actually rinsing dishes, showering, brushing teeth, etc.
Replacing older, standard water fixtures and appliances with newer, more water-efficient versions can make a tremendous difference in reducing your daily household water use. Leak-proofing your tank and water system is absolutely essential to ensure that your water lasts through the dry season. Two methods for leak proofing large-capacity water tanks are described below.
Option 1: Install a valve manifold on your tank to limit water loss in the event of leaks. The manifold divides the tank into sections so that only one section of the tank’s capacity can be drained at a time. It is best to divide your tank into a minimum of three sections so that the maximum loss will be one third of your tank.
Option 2: Alternatively, you can use a small tank for all of your water supply needs and manually fill the small tank from the large capacity tank as needed. If the small tank is isolated from the large tank, then the maximum water loss in the event of leaks is the volume in the small tank. Exposed pipes are a common cause for major loss of water from leaks. Burying your water pipes will protect them from most animal bites and the elements.
Optimizing Quality of Stored Water
The quality of water from long-term storage in tanks is primarily dependent on the quality of the source water, the tank itself, and the two critical storage conditions of temperature and light. To obtain drinking water quality from either long- or short-term storage, it is recommended that both a drinking water filter and UV purification cartridge be installed at the drinking water faucet to remove common bacteria and other organisms.
Incoming water quality is critical for long-term water storage. It is important to fill the tank when the water source is clear. Filtering the incoming water is best; otherwise, be sure to use a presettling tank that allows the clear water to be pumped from the top while the sediment collects at the bottom.
Cool storage temperature is also important for water quality, and large tanks keep water cooler than small tanks. Exposure to light is also a critical factor for water quality. All sunlight must be excluded from the tank because sunlight encourages algae growth and water quality deterioration.
Emergency Water Loss
The sudden loss of a large portion of stored water in the midst of the lowfl ow season is a serious problem for any household. But deciding to pump from the stream or river in order to refill the tank at that point would be potentially devastating for fish survival. In that circumstance, the most responsible choice you can make is to obtain the water you need to get through the dry season from a retail water supplier.
Fire storage requirements
Fire protection storage requirements may vary by county. In Humboldt County, homes in State Responsibility Areas for fire are required to maintain a reserve of 2500 gallons at all times to fight fire. If this reserve is not kept in a separate tank, your larger tank must be plumbed in such a way that the 2500 gallons will not be bled down by other usage. A 2.5-inch standard male fire hose adapter is required for access to this water.
Permits For Tanks and Water Storage
County installation requirements: permits or other requirements also vary for tank installation within different counties and for different zones within counties. Call your county building department to determine permit requirements for your location. In Humboldt County the following general requirements apply: grading permit, tank permit for those greater than 5,000 gallons, riparian setback requirements.
State Water Board permits: California requires an appropriative water right (or “small domestic use appropriation”) for water that will be stored longer than 30 days. The riparian water rights held by landowners who withdraw water from a stream that passes by or through their property allows only for direct diversion. A small domestic use appropriation registration can be obtained from the State Water Resources Control Board (SWRCB) if the applicant qualifies for small domestic use as defined by the SWRCB.
Fish and Game Code requirements: DFG has authority under Fish & Game Code section 1602 to regulate any water withdrawal that may have an impact on fish or other aquatic life. According to the Code, anyone who undertakes an activity that might “substantially divert or obstruct the natural flow of any river, stream, or lake” is required to notify DFG of this activity.