==Design, suitable conditions and design limitations==
In situ technology has been extensively used in northeastern Brazil, in the Chaco region of Paraguay, and in Argentina. It can be used to augment the water supply for crops, livestock, and domestic use. With the mechanization of agriculture, its use has diminished, but it is still recommended for regions where the volume of rainfall is small and variable. The approach used depends primarily on the availability of equipment, the nature of the agricultural and livestock practices, and the type of soil.
All rainfall harvesting systems have three components: a collection area, a conveyance system, and a storage area. In this application, collection and storage is provided within the landscape. Topographic depressions represent ideal collection and storage areas. In many situations, such areas are impermeable, being underlain by clay soils that minimize infiltration. Methods of rainwater harvesting in situ, including site preparation of agricultural areas in Brazil, are described below.
[[Image:in situ diagram.jpg|thumb|none|500px|Figure 1. Low Topography Rainfall Harvesting Areas (Tajamar). Source: Eugenio Godoy V., National Commission on Integrated Regional Development of the Paraguayan Chaco, Filadelfia, Paraguay.]]
Water stored in tajamares is normally used for livestock watering and may be used for domestic consumption after filtration and/or chlorination. Individual tajamares have also been used as a means of artificially recharging groundwater aquifers. Tajamares built in the Paraguayan Chaco have produced up to 6 800 m3/yr for aquifer recharge.
====Use of Furrows as Rainwater Storage Areas====
====The Guimarães Duque====
The Guimarães Duque method was developed in Brazil during the 1950s, and uses furrows and raised planting beds, on which cross cuts to retain water are made using a reversible disk plow with at least three disks. The furrows are usually placed at the edge of the cultivation zone.
==Costs, operation & maintenance==
This technology requires very little maintenance once the site is chosen and prepared. Maintenance is done primarily during the course of normal, day-to-day agricultural activities, and consists primarily of keeping the collection area free of debris and unwanted vegetation. Where only parts of the rows are cultivated, rotating the areas that are plowed will enable more efficient maintenance of the available storage area.
