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Question
what are the strategies to be taken note of in transformation of the agriculture with respect to hydrology and also the type.of technology to be  considered in areas of lack of technology like west Africa_ Nigeria.

Answer
Jennifer:

Sounds like a class question.  I like to help, but in most classes, questions have a context, by that, they are asked as part of, or following a discussion of the subject and are looking for as an answer, points brought up in the discussion.  Not being part of the discussion or privy to the materials you were assigned to read, I can offer some insight but it may or may not be what the professor is looking for.


First, ground water is dependent on the climate, surface water, geology, topography and natural vegetation present in the area.  Climate dictates the amount of annual rainfall and hence the total amount of available ground water as limited by recharge rates.

Surface water is an indication of availability of ground water too, since surface water and perennial streams indicates available ground water and its relative recharge and amount.

Geology dictates available aquifers or aquatards, their permiability, porosity, and depth.  It also controls how difficult it might be to drill to and recover it.

Topography controls where the groundwater occurs, whether exploitable areas are widespread or limited in extent.  Natural vegitation gives an indication of annual rainfall and available ground water.

For example in areas of the US groundwater has been appreciably altered by invasive species of cedar trees.  The trees have destroyed grasslands by lowering ground water levels throught year round transpiration.  They have also destroyed the thick soil and prairie grasses resulting in thinning of soils or eroding of them entirely, turning once lush grasslands into rocky scrub lands over large areas of central Texas.  South Africa has the same problem but with other invasive species, and have government teams that do nothing but kill the invasive water hog species of trees in order to preserve the ground water levels.

With respect to agriculture, when transforming agriculture, one must carefully consider the prevalent soil and the current agricultural crops.  Usually crops grown by locals have been selected for their suitability to existing soils and percipitation levels.  Transitioning to a cash crop means taking into consideration the water usage of the crop per acre to produce a normal crop.  This means irrigation well production needs to be such that it can meet the need without lowering the ground water levels to the point that it affects surface water.  For instance, if an aquifer can produce a certain amount and the pumping rate needed to grow the selected crop exceeds the sustainable pumping rate of the aquifer, it will deplete the aquifer.  If the aquifer is the same source supplying ponds and streams in the area, over pumping can lower the levels of the ponds and streams to the point that they dry up and are no longer available for livestock or human use.

Another thing to consider is the water chemistry of the ground water.  Using heavily mineral laden ground water for irrigation results in the build up of mineral salts in the soil that can make the soil unsuitable for agricultural use.  This is happening in agricultural areas of California.  This may take a long time, or can happen rapidly, depending on the climate and the ground water chemistry.

Irrigation runoff can also impact surface water and ground water as the runoff can concentrate pesticides and herbicides resulting in problems with indegenous wildlife as these chemicals are concentrated in surface water bodies.

Different irrigation methods use different amounts of water.  Drip irrigation, requiring more infrastructure uses a lot less water, spray and flooding use a lot more since losses to evaporation and run off are higher.  Flooding or running water down the troughs between the furrows is more ameanable to low tech and has been used in the middle east and Egypt for thousands of years.

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Keith Patton

Expertise

I can answer questions concerning physical and historical geology, environmental geology/hydrology, environmental consulting, remote sensing/aerial photo interpretation, G&G computer applications, petroleum exploration, drilling, geochemistry, geochemical and microbiological prospecting, 3D reservoir modeling, computer mapping and drilling.I am not a geophysicist.

Experience

I have 24 years experience split between the petroleum and environmental industries. I have served as an expert witness in remote sensing, developmental geologist, exploration geologist, enviromental project manager, and subject matter expert in geology and geophysical software development.

Organizations
American Association of Petroleum Geologists
American Association of Photogrammetrists and Remote Sensing

Education/Credentials
Bachelor and Master of Science
Registered Geologist in State of Texas

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