2007 Ground Water Summit

Wednesday, May 2, 2007 : 2:40 p.m.

Making the Connection: Joining the Rio Hondo and San Gabriel River Spreading Grounds for Maximum Operational Flexibility

Nancy Matsumoto, P.G., C.HG., Water Replenishment District of Southern California and Kenneth A. Zimmer, P.E., Los Angeles County Department of Public Works

The Water Replenishment District of Southern California (WRD or the District) manages two of the most utilized groundwater basins in Southern California, the Central and West Coast Groundwater Basins (CWCB).  The CWCB were adjudicated in the 1960s to limit groundwater production and to stabilize declining groundwater levels.  Since that time, natural recharge has been supplemented through artificial replenishment activities, including injection at coastal seawater intrusion barriers and surface spreading at percolation basins (“spreading grounds”).  WRD purchases imported and recycled water for these artificial replenishment activities, owns and operates several replenishment-related facilities, and works closely with the owners and operators of other such facilities within the District.

The Los Angeles County Department of Public Works (LACDPW) owns and operates the majority of the replenishment facilities throughout Los Angeles County.  Their Rio Hondo Coastal Basin Spreading Grounds (RHCBSG) and San Gabriel Coastal Basin Spreading Grounds (SGCBSG) are the primary locations for artificial replenishment in the CWCB.  The RHCBSG are fed from the Rio Hondo, while the nearby SGCBSG are fed primarily from the parallel San Gabriel River.  An average of 125,000 AF of water (consisting of imported, recycled and local water) is conserved between the RHCBSG and SGCBSG each year.

The RHCBSG and SGCBSG receive imported, recycled and local water from the same sources, but are not directly connected to each other.  This has led to missed opportunities for groundwater recharge, when one of the spreading grounds is available but the other is not.

WRD and LACDPW have worked closely together to identify and quantify these missed opportunities for groundwater recharge, so that an appropriate connection may be designed and constructed between the RHCBSG and SGCBSG to allow water to be shifted between the two spreading grounds as needed, thus improving operational flexibility and increasing the total amount of water conserved each year.

Nancy Matsumoto, P.G., C.HG., Water Replenishment District of Southern California Nancy L. Matsumoto, P.G., C.HG. is a Senior Hydrogeologist at the Water Replenishment District of Southern California. She holds a B.S. in Geology from Texas A&M University, and a M.S. in Geology from California State University – Los Angeles. Ms. Matsumoto has over seventeen years of professional experience in the water resources management, water resources consulting and environmental consulting fields.

Kenneth A. Zimmer, P.E., Los Angeles County Department of Public Works Kenneth A. Zimmer, P.E. is a Civil Engineer at the Los Angeles County Department of Public Works. He holds a B.S. in Civil Engineering from San Diego State University. Mr. Zimmer has over seventeen years of professional experience in flood control and water conservation planning, design, and operations.


The 2007 Ground Water Summit