Water Budgets

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Each Household is Unique

Each household uses water differently depending on the number of residents, parcel size, amount and type of landscaping, and limited special considerations. In order to tailor water usage to individual households and still achieve state mandated water use regulations, the Las Virgenes Municipal Water District has adopted a water budget based billing system that allows for maximum individual flexibility while also encouraging efficient water usage.

Your  Unique Water Budget

Your water budget is based upon three household uses of water: 1) Indoor Use, 2) Outdoor Use and 3) Special Adjustments that may be appropriate for your household.

 Your water budget is equal to:

Indoor Need is based on providing each person in the household with a standard volume of water. The current California standard is 55 gallons per person per day.

Outdoor Need is determined by using the customer’s irrigated area and local weather data to determine the efficient volume of water to support healthy plants and a modest amount of turfgrass. This amount will change from month to month as weather changes.

Adjustments will be made for special situations such as medical needs, licensed child/adult/health care providers and caring for horses or livestock.

Your water budget is based upon formulas for indoor and outdoor water usage unique to your household. To develop your water budget, the following formulas are applied to your household based upon information unique to each household.

Your Indoor Budget

Your indoor budget is calculated using three factors:

  1. 55 gallons of water per person per day
  2. The number of residents in your household
  3. The number of days in a billing cycle

Your indoor budget is based upon the number of residents in your household. This information is provided to the District by customers or a default value of three residents is used when this information is not provided. The number or residents is then multiplied by an indoor efficient 55 gallons of water per resident per day. Billing cycles may have a different number of days in the cycle so this number is multiplied by the number of days in any given billing cycle. Finally, this number is then divided by 748 which is the number of gallons in a unit of water.

This calculation is performed each billing cycle based upon the following formula:

Water Budget Indoor equation

Your Outdoor Budget

Your outdoor water budget is calculated using three factors:

  1. Irrigated area per parcel, including pools and spas
  2. Daily evapotranspiration (ET)
  3. Plant factor

The irrigated area is the amount of landscaped area on your property that receives regular watering. This area was initially determined through the use of areal imagery and processing to identify the areas on your property that appear to be irrigated. However, this process could be affected by landscape features such as tree canopies so it is important for you to verify that this area has been correctly determined for your property. Also please contact the District when you change your landscaping as this could affect your irrigated area as well. Pools and spas are also included in this factor as they need to have water regularly added to compensate for water loss as a result of evaporation.

Evapotranspiration (ET) is the amount of water lost each day in landscaped areas as a result of evaporation and plant transpiration. You can also think of ET as plant water demand as this factor is based largely on the amount of solar radiation (sunlight) that your plants receive each day which also drives the amount of water a plant needs to recover each day. This factor changes daily based upon cloud cover and fog. Keep in mind that this factor changes dramatically with the seasons as the length of day and angle of the sun vary with the seasons. As a result, plants need much less water in the fall and winter than they need in the spring and summer. Make sure you adjust your irrigation seasonally to compensate for the change in ET over the year.

The plant factor is the amount of water required by different plant types. The District applies a plant factor of 0.8 to your outdoor budget. By comparison, seasonal turf has a plant factor of 1.0 since it is a water intensive type of vegetation while native plants will typically have a plant factor below 0.5. The plant factor of 0.8 is applied in recognition that typically not all of properties use all turf in their landscaping. This plant factor is also used to encourage property owners to use water efficient and climate appropriate landscaping so that state mandated water efficiency standards can be achieved.

Finally, a couple of conversions are completed to convert irrigated areas and ET values into gallons and then into units of water which is ultimately the billing unit of water delivered to your home.

This calculation is performed each billing cycle based upon the following formula:

 

Special Adjustments

Customers can also request special adjustments to their water budget when special circumstances or needs are identified. This could include providing additional water to your indoor budget for residents that are home for longer periods such as elderly care or hospice services. Also included as a special adjustment could be additional water needed in your outdoor budget to provide water for livestock and associated facilities.

Please contact the District if you think you might be eligible for a special adjustment as this are provided on a case by case basis.  

Water Budget Indoor plus Outdoor plus Adjustments

Water Based Billing

Water use within the monthly water budget will be considered efficient and billed at the lowest rates. Use above the water budget will be considered inefficient or even wasteful, based on state efficiency standards, and billed to recover the higher cost for the agency to deliver that amount of water to the customer.