Problem:  In many regions of the world low annual rainfall and poor distribution of rainfall throughout the year lead to low crop yields that are often unreliable.  
Solution:  The use of microcatchments as a water harvesting method greatly increases crop productivity, and have been used for thousands of years.  




 
History
Microcatchments were first used in the Negev Desert of Israel, during the reign of King Solomon between the tenth and sixth centuries B.C. The people cleared the hillsides to increase runoff and built rock walls along the contours to collect and built ditches to convey the water to lower fields.  Large scale water harvesting methods helped to propel the agriculture to an astounding level in a region with an annual rainfall of 3-4 inches!!

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  Figure 1:  Negev Desert of Israel

Technical
Microcatchments are simply ditches that concentrate surface runoff around the plant, thus reducing runoff and increasing infiltration to the plant roots. An example of a microcatchment can be see in
Figure 2, the arrows indicate the direction of runoff flow.

Figure 2:  A successful microcatchment design in Isreal (Dryland Forestry)

Main Technical Characteristics:

•   overland flow harvested from short catchment length
•   catchment length usually between 1 and 30 meters
•    runoff is stored in soil profile
•   ratio of catchment area to cultivated area is usually 1:1 to 3:1
•   normally there is no provision for overflow

Benefits:

• increase in crop yield and reliability
  
• allow plants to grow in otherwise unsustainable conditions
• augments existing water supplies
  
• cheaper than installing expensive irrigation system

Limitations:

• requires deep soil (at least 1.5 to 2m) in cultivated area to store water between rainfall
• require at least 80mm of precipitation per rainy season if the season occurs during the cold season, and requires more than 80mm if rains occur during the summer due to greater evaporation
• soils in the catchment area must be crust-forming or impermeable
• soils in the cultivated area need to have a high water capacity

Further Investigation:
Check the reference lists within articles and books for even further reading

Prinz, Dieter. "Water Harvesting for Afforestation in Dry Areas."  Institute of Water Resources Management.  Karlsruhe, Germany

Elevitch, Craig and Kim Wilkinson. "Microcatchment:  Making the Most of Limited Rainfall."  The Overstory: Agroforestry ejournal, 1999-2004

Shanan, L. Tadmor. Micro-catchment Systems for Arid Zone Development: a handbook for design and construction. Jerusalem:  Hebrew University, 1979

Bainbridge, David A. "Microcatchment Water Harvesting."  ecomposite.org: 2003

References:
Fidelibus, Matthew W., and David A. Bainbridge. "Microcatchment water harvesting for desterevegetation."  California Department of Transportation, 1994

More Water for Arid Lands. Washington D.C.:  National Academy of Sciences, 1981

Ffolliot, Peter F, et al. Dryland Forestry:  Planning and Management. New York:  John Wiley and Sons, Inc., 1995

Weber, Fred R.  Reforestation in Arid Lands.  Arlington:  Volunteers in Technical Assistance, 1986

Critchley, Will and Klaus Siegert.  A Manual for the Design and Construction of Water Harvesting Schemes for Plant Production.  Rome:  Food and Agriculture Organization of the United Nations, 1991