Exchanges of cations between the soil and the irrigation water are the start of soil salinization.

What are the preventive solutions: is it possible to to avoid water becoming brackish?

In search of the causes of saline irrigation water… elevation of the salt concentration of irrigation water may be the result of human actions upstream of the irrigated area, such as deforestation.

What are the curative solutions: how can brackish irrigation water be dealt with?

• increase in the frequency of irrigation, increase the water supply to plants taking into account the requirements for leaching and/or other water sources;
• rehabilitation through modification of farming practices;
• artificial surface drainage;
• artificial vertical subsurface drainage;
• artificial horizontal subsurface drainage.

• Irrigated agriculture modifies the water balance created between rain and river flow, on one hand, and between groundwater, evapotranspiration and transpiration on the other.
• Irrigated agriculture contributes to a shallow water table.
• Bad management of the transport and application of water (losses), but also the requirement of leaching, which implies a supply of water greater than that needed by the plants, lead to a rise in the water table towards the soil surface.
• The water table limits the depth to which salts are leached.
• The evapotranspiration demand may be drawn directly from the groundwater; the water loaded with leached salts is carried upwards by capillary rise. During this rise the water continues to evaporate, concentrating the soil solution. This is the process of evapoconcentration. This phenomenon not only cancels out the leaching process, but carries the salts back to the upper soil level, the most sensitive region in terms of plant growth.
• Groundwaters at the perimeter of irrigated areas are often rich in soluble salts. On one hand they collect the water leaching the salts, and on the other hand, as they rise they can remobilize salts from deep layers, which precipitate on the surface through the process of evapotranspiration.

What are the curative solutions?

• lowering the water table:
  • by raising the level of the land;
  • with an artificial horizontal drainage system;
• rehabilitation through modification of farming practices: leaving land fallow and working the soil, using salt-resistant plants;
• biodrainage.

Overpumping of freshwater from coastal groundwaters can lead to depressions, which fill with the neighbouring seawater. Seawater penetrates through the subsoil due to the difference in density (seawater contains on average 30 grammes of salt per litre and is therefore denser than freshwater). This phenomenon is called saline intrusion. This intrusion, beyond a natural level of weak penetration is almost certainly the consequence of an overexploitation of the aquifer.

What are the solutions?

• limited drawing of the groundwater.
• recharging of the groundwater (example: the town of Agadir).