You have to solve a soil-water balance method by taking into account the different terms (incomes and outcomes) of the water balance. Typically there is one one income which is the precipitation (it might be corrected by the intercepcion). The outcomes depend on the water availability in the soil and the potential evapotranspiration (PET). From the complexity perspective, evapotranspiration is the key factor. To estimate PET I would say that Thornthwaite is the easiest way. This method is very simple and depends on a very few parameters (the mean temperature, the day of the year and its length, etc). Due to this simplicity very often this method is not the most suitable one. If you had enough data for using of thePenman–Monteith method you should explore this way.

Hi Ibraheem,

in order to recommend you a suitable method i would liek to know what kind of datas are available to calculate groundwater recharge and on what scale you are working.

Hello

Thank you all.

I have the rainfall data, Pan-A evaporation data and the Min, Max temperature.

I'm working in small scale catchment area.

Hi Ibraheem,

At a link below You can find some models for calculating runoff/infiltration...

http://hydrology.usu.edu/RRP/userdata/4/87/RainfallRunoffProcesses.pdf

You can perform well inventory and pumping test to estimate the recharge potential of Aquifer.

Thank you very much

One of the basic methods to determine groundwater recharge is the water balance equation (do you have measurements of runoff?).

No. this the problem that in the area there is no runoff measurement.

in some articles I saw that they use direct equation by using the precipitation amount only.

Some overview about vadose zone techniques to estimate recharge.

https://www.soils.org/publications/sssaj/abstracts/58/1/SS0580010006

Hello, you could use the Bagrov method, described on http://www.small-scale-hydrology.de/. The method estimates real evapotranspiration and groundwater recharge from rainfall data, potential evapotranspiration, depth to groundwater and some soil information.

Good luck

Klaus Bohne

My PhD thesis is on Ground Water Recharge Management in Saurashtra, India: Lessons for Water Governance. It deals with recharge methods, estimations and develops correlation between rainfall and recharge rates.

To download, you may visit: https://wur.academia.edu/SrinivasMudrakartha

Dr Srinivas Mudrakartha

You can try the water table fluctuation method (WTF) if you can obtain the specific yield of the soil in the vadose zone.

http://water.usgs.gov/ogw/gwrp/methods/wtf/

Using Curve Number or Hydrologic Soil Cover Complex method one can easily estimate the recharge capacity of the soil.

A series of Monitoring wells between the Mountains and the river which

would have elevation data recorders, or electronic sending units so you can

watch the change in ground water elevations as the river and streams

rise and fall.

A very large portion of the water flows through the ground down hill

parallel to the streams that feed the larger rivers.

thank you all

I can't stress highly enough that choosing an appropriate recharge estimation technique depends on a good conceptual model. Without understanding the dominant hydraulic processes controlling recharge you cannot hope to derive reasonable estimates. Also, in my experience, empirical equations simply relating rainfall to recharge are not transferable from area to area. Rick Healy has written a recent textbook which outlines techniques which i would recommend: http://www.amazon.com/Estimating-Groundwater-Recharge-Richard-Healy/dp/0521863961

Indeed! I fully agree with M.O.Cuthbert

thank you all for your valuable answers.

Cuthbert's view is perfectly in order.

I have a series of only precipitation data, how can I get the net groundwater recharge. Thanks

A strange thing I recently ran into relates to " e " and " e + 1 "

If you take a cube of soild rock at a given specific gravity, and crush it,

mix it, and put it back together it will increase in volume from 100 % to

about 136.788 1815 %. This is the ratio of ( e + 1 ) / e. The result is

that without compression, crushed rock in streams that is well graded

has a volume that is 73.105 731 % rock, and 26.894 2689 % Voids to

a rediculous number of digits. At its best it would be nearly 73.1% gravel and sands, and 26.9% Voids full of water. As you go deeper down into the

layers it would become more compressed and more clogged with fine particles, so it would be more rock, and less voids down to where you

encounter solid bedrock of 100% rock, and 0 % Voids.

You could treat this like an exponential decay curve where it begins at

26.9% Voids full of water, decreasing down to 0 % Voids at and below the

bedrock.

Using this you can determine the total volume of water in a vertical

column of gravel that is 1 meter x 1 meter x N meters tall between

the top of the ground water - water column and the bed rock..

The area under an exponential growth curve between H = zero,

at bedrock, and H = N meters at the water table would be the area

under the curver of the integral of X^e which when intergated would be

1 / (e+1) which is also 0.268941421 between zero and H.

Now If I have not screwed this up, the integral of the voids would be

H X ( 1/(e+1))^2 which would be 0.072329488 H.

Now if I have not blown the logic, the maximum water Volume would

be less than or Equal to 7.233% of " H " cubic meters of water

in a one meter by one meter square between the bedrock and the ground water table when H is very tall. When H is very short, it could reach a maximum of 26.9% water in a very short column of gravel and sand that is well graded. Again the ratio is 26.8941421 divide by 7.2329488 which is

3.718281828 :1 Maximum to Minimum ratio as H increases from say

H = 1 ( shallow ) to: H = a very large depth ( a deep aquifer ).

An aquifer could be any where within 17.063 545 45 +/- 9.83 059 665 %

Voids depending upon the magnitude of H, and the materials that make up

the sands, gravels, and soils in the acquifer. Rounding would give

17.06 +/- 9.83 % Voids in a water filled aquifer.

Any body want to cross check these numbers based on actual data ?

Recharging the ground water is very dependent upon the soil mechanics,

and the permeability of the soil. when you transition from gravels to sands to clays to Fat Clays to shales, the permeability decreased by several orders of magnitude. The voids decrease, and the ability of water to flow thru soils decreases by several orders of magnitudes as the particle sizes decrease, and the void spaces get smaller and smaller. Eventually the flow

rates are so slow that they are essentially zero. This is the type of materials that are used to line land fills, and make the cores of dams to keep them from leaking water.

Water can also flow up to 10 times faster horizontally in the mixed sands and gravels, and smaller materials than it flows vertically. This has to do with both the properties of water ( a polar molecule ), and the properties of the soils. clays are tabular ( flat like stacked tables laid flat atop one another ). The water can flow much faster horizontally thru the tables, than it can flow vertically, because it must find its way down around each table.

If you want to recharge an acquifer, drill holes down thru the layers, and fill the holes with sand or gravel. Also a small dam can be used to pond the water around the drilled areas. To recharge an acquifer, you need to store the water so it can soak into the ground. It is all about time. Water that runs off down a stream does not have time to soak down into the ground.

Water that s ponded like in lakes, and basins, and rivers with shallow gradients has the key element time. Lots of time is needed for water to

move both horizontally and vertically. It can actually take from days to weeks for a water table to increase down near a river valley, if it rained heavily up in the mountains. The river may flood in a few hours, but it takes much longer for water to move downward, accumulate atop the sloped ground water table, and flow miles ( kilometers ) down gradient.

If we all want to live in the current changing climate, we must store lots of water, and lots of smaller reservoirs are better than a few big ones.

Think about Snow versus Rain. The melting of Snow is a very long and time consuming process, so there is lots of time for the water to soak into the ground, and migrate downward to the water table. So we as Humans need to mimic nature by storing water , lots of water is large shallow basins, so it has time to slowly move down to the water table. The problem is that larger basins use up lots of land that we need for agriculture to grow food that also needs the water.

I would suggeast reading two Books called 1491, and 1493. The South Americans, the Aztecs, the Myans, Toltecs, the Mixtecs , and native peoples of the Mississippi River Valley had figgured out how to use water in large shallow basins with elevated causeways to hold water and grow all kinds of food, and trees. There were around 75 million of them in the Americas until the Spanish, and the Portugese introduced diseases carried in Pigs, and, Humans from Europe. More then 95 % died from these diseases. The results were incredible jungles where crop lands used to grow food. The Cambodians also did similar things, and then they also dissappeared. The Chinese used terracing to pond water, and grow rice.

The Peoples of Chille, and Bolivia used lots of canals side by side so the Sun could warm the water at day, and keep the ground warmer at night so the plants did not freeze in the high altitude climates.

Please I have rainfall data and water table depth data, how can I calculate net recharge.

Think about a basin from a historical basis. The ground water table is the top elevation of a Volume of water that has a width, length, and depth, a percentage of soil, a percentage of gravels, and a percentage of free space filled with water. Now it has taken thousands, or tens of thousands of years for that basin to have achieved a equilibrium condition where the

inflow rate, and the out flow rate are essentially equal. So, if you know the summation of the rain fall in inches of rain per year, then you also know the outflow rate in evaporation, plus horizontal transport, plus the amount that moves down slope to exit the system. Now if the system is having ground water pumped out of it for irrigation, and the water table is falling,

the system will eventually go dry, unless, you construct dams, and the associated reservoirs, so the amount of water entering the system is greater than or equal to the amount of water being pumped, plus the amount that leaves naturally.

Try to think about the problem on a smaller scale, like a five gallon bucket full of water, and what it weighs, and a five gallon bucket full of compacted soils, and what it weighs, and that same five gallon bucket full of soil, and then saturated with water, and what it weighs. Then you can calculate the

weight, and thus the percent of water in the system (bucket). Think of the bucket as a scale model of your basin, and you are only going to make changes to the top one inch of the soil in the bucket, where you add, and subtract water so the water table in the bucket can move up or down by

a set amount. So then, how much water does it take to fill up the last inch of soil in the bucket with water to saturate the soil. It will be less than one inch of water added to saturate the last inch of soil in the bucket, as the last inch can be anywhere from 50 % air voids (gravel), down to less than

10% air voids (mixed sand and clay). It may take from 1/2 Inch of water to 0.1 inch of water to fill up the last one inch of soil with water, and saturate the last one inch. Now your bucket model will never be as compacted as the native soil conditions in your basin, because it has had thousands of years to settle and be more compact, but, it will give you an idea of what

an inch of rainfall will do to the water table if the soil is permeable enough for the water to move down thru the soil.

I hope this helps you solve your inflow, outflow problem for recharge.

if you have thematic layer of lithology you can apply rainfall infiltration factor method, otherwise water table fluctuation method can be apply. both are mentions in this text.

See http://www.small-scale-hydrology.de

You'll find a paper and two computer codes considering rainfall, potential evapotranspiration, soil texture, plant water uptake, capillary rise from groundwater table