O problema de drenagem dos solos na baixa Arone mapanga na Ilha de Inhaca

Abstract

In agriculture, water is intrinsic in the physiological processes of crops that culminate in the production of dry matter. However, water can be an equally “dangerous” agent when in excess. For example, river erosion, flooding of crops even in housing areas, leading to the construction of protective infrastructure, such as dikes, drain ditches, preferential channels to avoid disasters. On the island of inhaca there is a low-lying area known as “arone mapanga” which has been found almost every year with a high water table and some plots flooded. This low is seen as potential for the practice of agriculture if a drainage system is implemented. When referring to drainage, it is meant here the control of the water table and the flow of water. The present study aimed to find management measures to mitigate the drainage problem in the downtown area, having consisted in the determination of the drainage norm and hydraulic properties of the soils. In order not to invest “rivers of money” in a field with low agricultural potential, the suitability of soils was also determined. The drainage standard for the study area shows that the drainage problem is critical in February, but the hydraulic characteristics of the soil suggest that the soil is in a position to evacuate all water. After analyzing the infiltration, texture and permeability of the soils, the study reveals that the drainage problem is not related to the characteristics of the soil, but may be due to its geomorphological situation. Due to its proximity to the coast and its relief with the configuration of a hydrographic basin, there is a tendency for the water to flow downwards. Allied to this situation, the soils are sandy and very permeable, thus allowing fresh water to drain into the sea, the denser salt water tends to penetrate the aquifer, forming a wedge under the fresh water (water pocket inside the Island). The soil suitability results show that the soil does not justify a large technological investment due to its low agricultural potential