Point- and reach-scale measurements are important for determining accurate seepage rates in controlled flow channels

A critical component of water-resources management in the irrigated agriculture landscape, particularly those landscapes dependent on groundwater availability, is determining groundwater recharge rates from streams and other channels. In California, flows in many such channels are “controlled” by upstream reservoir releases to meet downstream urban, irrigation and environmental water requirements. Seepage volumes from these channels and how they might vary during controlled release periods is a key component of meeting downstream riparian and groundwater-pumping needs. Understanding annual seepage from streamflow channels is also important in developing water budgets as part of the management of groundwater resources under the Sustainable Groundwater Management Act (SGMA) in California. However, direct measurements of channel seepage rates are infrequent or unavailable, and these rates, or associated volumes, are most often only estimated. Here we describe direct point- and reach-scale field measurements of channel seepage rates in Lower Putah Creek (Solano County) and in distribution lateral channels of the Oakdale Irrigation District on the east side of the San Joaquin Valley (San Joaquin and Stanislaus counties). We measured overall average seepage rates of about 2 feet (610 mm) per day at both locations and determined how these rates varied spatially and temporally during the summer when channel flows are controlled for downstream requirements.

Application of New Concrete Materials in Channel Lining of the South-to-North Water Diversion Project

Concrete lining is commonly used in large channel project to fixup soil slope and prevent channel seepage. Concrete lining is a type of thin plates structure which should have the high compression strength, crack resistance and durability. Two new high performance concrete (HPC) are used in lining project of south main channel of Yellow River-crossing project in east-route of the South-to-North Water Diversion Project. One is flyash HPC with manufactured-sand and the other is HPC with cementitious capillary crystalline waterproofing material (CCCW); meanwhile, the mix proportion of flyash HPC with manufactured-sand and HPC with CCCW are recommended. For flyash HPC with manufactured-sand, the recommendatory water-binder ratio is 0.4 and the recommendatory flyash content is 30%. For HPC with CCCW, the recommendatory water-binder ratio is 0.48 and the recommendatory CCCW content is 1.5%.With the wide application of new HPC, the compression strength, crack resistance and durability of lining concrete are improved, channel seepage discharge is reduced and a large amount of natural building materials are saved.