# What is the water balance equation?

## What is the water balance equation?

A general water balance equation is: P = R + ET + ΔS. A water balance can be used to help manage water supply and predict where there may be water shortages. It is also used in irrigation, runoff assessment (e.g. through the RainOff model), flood control and pollution control.

What is a water balance diagram?

A water balance chart compares the total water supplied to the site, the actual water consumed within all the water end uses in the site, and the total water leaving the site. This will help to identify areas of significant water usage and problem areas, including leaks and uncontrolled losses.

How do you calculate evapotranspiration?

Crop evapotranspiration is calculated by multiplying ETo by Kc, a coefficient expressing the difference in evapotranspiration between the cropped and reference grass surface.

### How hydrologic equation and water balance are related?

In hydrology, a water balance equation (hydrologic equation) can be used to describe the flow of water in and out of a system. A system can be one of several hydrological domains, such as a river, column of soil, drainage basin, reservoir, and the like.

What is water balance components?

Water balance components were divided into two separate parts including: ( ) precipitation and evaporation over the lake surface leading to the direct inflow and outflow from the lake, which were calculated during the 12 months of year 2005, and the lake basin water balance when the difference between precipitation (P) …

What is standard evapotranspiration?

Crop factors Crop evapotranspiration under standard conditions (ETc) refers to the evaporating demand from crops that are grown in large fields under optimum soil water, excellent management and environmental conditions, and achieve full production under the given climatic conditions.

#### What increases evapotranspiration?

Relative humidity: As the relative humidity of the air surrounding the plant rises the transpiration rate falls. It is easier for water to evaporate into dryer air than into more saturated air. Wind and air movement: Increased movement of the air around a plant will result in a higher transpiration rate.

How do you calculate water outflow?

To calculate the water flow (in m3/s) multiply the average water velocity by the average cross-section. To express this water flow in litres per second (l/s), multiply the result (in m3/s) by 1000. 0.486 m3/s x 1 000 = 486 l/s.

What are the consequences of poor water balance?

If you do not take in enough fluids or water, you become dehydrated. Your body may also have a hard time getting rid of fluids. As a result, excess fluid builds up in the body. This is called fluid overload (volume overload).

## What regulates water balance in the body?

The kidneys can regulate water levels in the body; they conserve water if you are dehydrated, and they can make urine more dilute to expel excess water if necessary. Water is lost through the skin through evaporation from the skin surface without overt sweating and from air expelled from the lungs.

How does evapotranspiration affect the water balance equation?

Evapotranspiration (ET c) is the biggest subtraction from the water balance equation (Equation 2). The ET c changes throughout the growing season due to weather variations and crop development. Crop water use or ET c depends on many factors.

What is the equation for water balance in hydrology?

HYDROLOGY – WATER BALANCE. Water balance equation Æ. R = P -ET -IG -ΔS. where:P= Precipitation. R= Runoff. ET= Evapotranspiration. IG= Deep/inactive groundwater ΔS= Change in soil storage Inter-relationships between components Variation of components with time.

### How to calculate crop specific evapotranspiration ( ET C )?

Crop Evapotranspiration (ET c) can be estimated using a two-step approach to determine the crop-specific water use (ET c) as per the following equation: ET c = ET ref x K c (Equation 3) Where ET ref is the reference evapotranspiration – which is the evapotranspiration from a reference crop (grass or alfalfa) – and K c is the crop

How does an evapotranspiration based irrigation system work?

Evapotranspiration-based irrigation scheduling or water-balance method The status of the soil water for an irrigated crop needs monitoring regularly to assist the irrigation manager in making irrigation decisions. Typically, irrigation scheduling can be done in two ways. One is by directly monitoring soil-water by using soil moisture sensors.