Conclusions

The results of the study show that the irrigation system infiltration is the main groundwater replenishment mechanism. About 70% groundwater recharge comes from canal loss and about 20% recharge comes from field infiltration. The groundwater from irrigation area to non-irrigation area is about 70% of non-irrigation area recharge and acts as subsurface drainage for irrigation area. It desalinates the irrigation area and supplies water to non-irrigation area. The salt that is moved to non-irrigation area following subsurface drainage is about 75% of the salt that is moved to riverway following surface drainage. Recharge from irrigation system increase but the recharge per irrigation area decreases from 1980s. This indicates the water resource saved from water use efficiency improvement was consumed by the waste land reclamations. As the water use efficiency improved in the study area, subsurface drainage decreased and lessened groundwater to non-irrigation area. It might be the reason that causes the wetland shrinking.

The flooding of the Akesu River is a supplemental groundwater replenishment mechanism. Lower TDS flood flushes the alluvial plain in summer and higher TDS regeneration water brings salts from irrigation area back to river in winter. The river desalinates the alluvial plain and flushes away about 710 thousands ton salt annually.