Total Infiltration by Horton's Equation

Problem

To calculate the total infiltration and total runoff for a certain catchment

Given,

Initial Infiltration Capacity(Fi),Final Infiltration Capacity(Ff),Horton's Constant,Time(T)

Solution

Calculate Total Infiltration.Then assume the evaporation loss as some constant.Subtract both of them from Precipitation to get the Runoff.

Methodology

1.Visit "Total Infiltration by Horton's Equation" Calculator

2.Put the given Initial Infiltration Capacity(Fi),Final Infiltration Capacity(Ff),Horton's Constant,Time(T)

3.Click Calculate.

k is often given in per day.You must convert it to per hour if the time period and Fi,Ff is given in hours.

Calculator is based on the integration of Horton's Equation

Volume of Evaporation

Problem :

To estimate the monthly evaporation loss

Given :

Reservoir area at the beginning and ending of the time period (eg : 1 month or 1 year)

Pan depth : 15cm

Solution :

You have to calculate the volume of evaporation.

Methodology

1.Go to Volume of Evaporation Calculator

2.Put the values of reservoir area at the beginning(IR) and ending(FR) of the time period

3.Pan depth(h)

4.Assume a value of pan coefficient(k) : k : 0.7(generally)

5.Click 'Submit'

6.You will get the evaporation of month May.Now calculate for all the 12 months.This will give a clear estimation of monthly pan evaporation of the reservoir.

The calculator calculates the volume of evaporation with the help of following formula :

= (k*h/3)*(IR+FR+Square Root of IR*FR)

Potential Evapotranspiration

Evapotranspiration (ET) is the sum of evaporation and plant transpiration. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies Transpiration accounts for the movement of water within a plant and the subsequent loss of water as vapour through stomata in its leaves. Evapotranspiration is an important part of the water cycle.

Potential evapotranspiration (PET) is a representation of the environmental demand for evapotranspiration and represents the evapotranspiration rate of a short green crop, completely shading the ground, of uniform height and with adequate water status in the soil profile. It is a reflection of the energy available to evaporate water, and of the wind available to transport the water vapour from the ground up into the lower atmosphere. Evapotranspiration is said to equal potential evapotranspiration when there is ample water.

Estimation of ET

Evapotranspiration may be estimated by creating an equation of the water balance of a catchment (or watershed). The equation balances the change in water stored within the basin (S) with inputs and exports:

The input is precipitation (P), and the exports are evapotranspiration (which is to be estimated), streamflow (Q), and groundwater recharge (D). If the change in storage, precipitation, streamflow, and groundwater recharge are all estimated, the missing flux, ET, can be estimated by rearranging the above equation as follows:

The most general and widely used equation for calculating reference ET is the Penman equation. The Penman-Monteith variation is recommended by the Food and Agriculture Organization. The simpler Blaney-Criddle equation was popular in the Western United States for many years but it is not as accurate in regions with higher humidities. Other solutions used includes Makkink, which is simple but must be calibrated to a specific location, and Hargreaves. To convert the reference evapotranspiration to actual crop evapotranspiration, a crop coefficient and a stress coeficient must be used.

Automatic PET Calculator Available

A very small script is created to calculate the potential evapo-transpiration(ET) with the help of Penman's Equation(PE).PE is a big equation and needs tedious and careful calculations to find the ET.But this calculator will help anyone to find ET by PE at a click of a button.


In hydro power plants thorough knowledge of ET is needed to estimate the storage of the reservoir and hence discharge.

Relation between P,Q and H

Now, P is directly proportional to both Q and H.

If either H or Q is increased the magnitude of P increases.If H is increased ,Q decreased,P increases but if H is decreased,Q is increased,P decreases.Visit HPC and try to find hydropower(P) with varying head(H) once and varying discharge(Q) once.Then vary both Q and H . Below is what I had done :

H(m) :100 : 150 : 200 : 250 : 100 : 100 : 100 : 80 : 60 : 150 : 200

Q(mcs) : 100 : 100 : 100 : 100 : 150 : 200 : 250 : 300 : 350 : 300 : 250

P(kW) : 98000 : 147000 : 196000 : 245000 : 147000 : 196000 : 245000 : 235200 : 205800 : 441000 : 490000

So H is more influential than Q on P.

Problem : 1 : Calculate the potential hydropower of a stream

Calculate the potential hydropower of a stream with a head of 300 m and discharge carrying capacity of 25 cubic meter per sec.

A stream with a discharge carrying capacity of Q cms and head of H m has a potential power P which is expressed by the equation :

P = wQHm kg/sec = 13.33QH hp = 9.8QH kW

The above problem can easily be solved with the Power equation.

But instead of calculating manually one can use the Hydro Power Calculator .

Just give a visit to the calculator,write the value of Q,H and w(specific weight of water) and click 'Calculate'.

Potential Power will be calculated and given in mkg/sec.

To change the result into horse power just change the unit to 'hp' .The output will be given in kiloWatt if hp is changed to 'kW'.

For a more detail physics you can visit the answer of hydro power in Answer.com

The Hydropower Calculator