AWWA SOURCES55706

The West Coast Basin Barrier Project, in operation for about 40 years, which has used recycled water as a part of injected water for 5 years, demonstrated the efficiency of the barrier to prevent seawater intrusion and overcome aquifers overdraft. To improve and consolidate this water conservation practice, the main goals of the performed study are to better understand the aquifer's hydraulic behavior and inland salt plumes dynamics, as well as to optimize barrier management and water quality control. To achieve these objectives, a tracer study using boron isotopes was carried out to demonstrate the relevance of this methodology as an appropriate tracer. Boron isotopes were chosen as the most appropriate, natural and low cost tracer. The results of the sampling demonstrated the possibility to distinguish the specific fingerprints of different water types, including recycled water. These fingerprints, in addition to the variable proportions of recycled and imported water injected in the barrier, allow tracking the hydraulic behavior of the aquifers. It is important to stress that aquifer recharge management and water quality control require the application of reliable modeling tools. The new 3D GIS Wingeo model demonstrated good performances and ability to simulate water quality evolution and to estimate water loss to the sea and salt intrusion. The simulations indicated that saltwater intrusion occurs easily in the deeper layers of the aquifers, allowing an increase of salt concentrations when injection diminishes. The results of the tracer study confirmed this hypothesis. It was concluded that the boron and its isotopes in conjunction with the concentrations of Sr and chlorides can be used for the monitoring of injected water and, simultaneously, to check the influence of saltwater intrusion. To obtain higher precision in determining aquifer behavior, however, monthly sampling is recommended for a period at least of half to one year. Includes 13 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

01/01/2002

Number of Pages:

18

File Size:

1 file , 950 KB