Abkhandari (Aquifer management): a green path to the sustainable development of marginal Drylands

Abstract

Recurrent droughts and occasional floods are the facts of life in drylands. The presence of innumerable societies in deserts is the living proof that even the extremely dry environments are livable; the secret is how to adapt to the situation. Floodwater management, the most important art of sedentarized desert dwellers, is the secret of living with deserts. Floodwater irrigation alone, or in combination with the artificial recharge of groundwater (ARG), has sustained the Persians for millennia. The scientists at the Kowsar Floodwater Spreading and Aquifer Management Research, Training and Extension Station in the Gareh Bygone Plain have been working since January 1983 to revive this ancient art and upgrade it to the level of science. A summary of important findings is provided as follows:

• 1. Debris cones and coarse alluvial fans are the best places for the ARG as they provide the potential aquifer for groundwater storage. The recharged water may be used for irrigation on the lower lying, fine alluvium;

• 2. Flood is not a proverbial curse but a blessing in disguise, and the turbid floodwater is the best resource for the sustainable development of drylands;

• 3. Translocation of fine clay minerals eventually makes the vadose zone impermeable. Planting deep-rooted, drought-resistent trees and shrubs, and introducing sowbugs (Hemilepistus shirazi Schuttz) are reliable methods to increase infiltration rate and the saturated bydraulic conductivity of the ARG systems;

• 4. The moving sand stabilization is best achieved by spreading turbid floodwater onto them. Establishing of living windbreaks and planting of fodder trees and shrubs turn a sand menace into a verdant pasture;

• 5. The 10 year average of native forage yield in the ARG systems has been 445 kg·ha⁻¹·year⁻¹ as opposed to 92 kg·ha⁻¹·year⁻¹ for the control. At 4×4 m² spacing,Atriplex lentiformis (Torr.) Wats. can annually yield 1500 kg ha⁻¹ of dry matter and support 3 heads of sheep;

• 6. The stem- and fuel wood yield of 18 year oldEucalyptus camaldulensis Dehnh. in the ARG system have been 4,684 and 781 kg·ha⁻¹·year⁻¹, respectively. The mean annual carbon sequestration of this tree has been 2.975 tons per ha;

• 7. Up to 80% of the diverted floodwaters reach the unconfined aquifer. As evaporation practically wastes large volumes of water in surface reservoirs, storing water underground is logical in deserts;

• 8. The high evaporation rate, the large sediment load, the environmental hazards, the undesirable social costs, the long time needed for the different phases of study, and the very large price tag make dam building the mosthydro-illogical choice in deserts where the ARG is practicable;

• 9. Each 5.5 ha of the irrigated farm provides income for a family of 7.64 member and 0.38 employment opportunities for a farm hand. On average, 4-ha of an ARG system provides one full time job for irrigation farmers. The benefit: cost ratio for this project is 22;

• 10. The number of wells in the area affected by the ARG activities has increased 10-fold to 130 wells, the irrigated area has increased 8-fold to 1,193 ha, and 345 job opportunities have been created in 4 villages that surround the Station.