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Also known as surface runoff, it refers to the flow of water that travels over the surface of the soil and does not infiltrate into the soil. In hydrology, there are several formulas and methods for calculating runoff. being this the most used:

Runoff Coefficient (CN) Method:

The runoff coefficient (RC) method is commonly used in hydrology and is based on the classification of watersheds based on their characteristics, such as land use, vegetation cover, and soil type. The general formula is:

Runoff = P * CN / 100

Where:

Runoff is the volume of runoff water in the basin (usually in millimeters or cubic meters).

P is the effective precipitation, that is, the amount of rain that contributes to runoff (in millimeters).

CN is the runoff coefficient, which varies depending on the basin classification and can range from 30 to 100 or more. Higher CN values ​​indicate higher runoff.

The value of the runoff coefficient (CN) is determined using tables or formulas that consider vegetation cover, soil type, infiltration and other factors of the basin.

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There are several formulas and methods to calculate potential or actual evapotranspiration, depending on the availability of data and the precision required. One of the most common methods for estimating evapotranspiration is the Penman-Monteith Equation method, recommended by the Food and Agriculture Organization of the United Nations (FAO) and widely used throughout the world, and the equation is The next:

ET0 = 0.408 * Δ * (Rn - G) + (γ * (900 / (T + 273)) * U2 * (e_s - e_a)) / (T + 273)

Where:

ET0 is the reference evapotranspiration (in millimeters per day).

Δ is the change in vapor pressure in air with temperature (in kPa/°C).

Rn is the net radiation at the surface (in MJ/m²/day).

G is the heat flux in the ground (in MJ/m²/day).

γ (gamma) is the psychrometric constant (approximately 0.066 kPa/°C).

T is the average daily temperature in °C.

U2 is the wind speed at 2 meters above the surface (in m/s).

e_s is the saturated vapor pressure (in kPa) at temperature T.

e_a is the actual vapor pressure of air (in kPa).

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Groundwater recharge = Effective precipitation - Evapotranspiration - Surface runoff - Groundwater withdrawal + Water flow from surface sources

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Methods for calculating the hydrological balance

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Methods for calculating the hydrological balance

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*Determination of groundwater recharge.

* Estimation of evapo-transpiration.

* Estimate of runoff.

* Infiltration estimate.

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The hydrological balance must be maintained and thus be able to carry out an assertive control of water management, it can be used for the analysis of floods or droughts, it is also used for the control of agriculture, deciding with this the best times to sow and for irrigating crops, if this balance is lost it can end up in a shortage of water and famine.

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It is the loss of water from the soil surface due to evaporation and transpiration from plants

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Factors Affecting the Hydrological Balance

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Factors Affecting the Hydrological Balance

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They are the variables that can affect the hydrological balance, which means that they can influence the amount of water available in an area and its distribution over time. Some of the factors that affect the hydrological balance are:

Vegetation

Climate

Topography

Floor

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The hydrological balance refers to the balance that is maintained in everything related to the management of water and natural resources.

It is a permanent balance between the water resources that enter a system and the resources that leave in a limited time.

The hydrological balance is used to schedule irrigation and make more efficient use of water