HR: 1340h
AN: H53C-1279    [Abstracts]
TI: Suspended Sediment Dynamics at the Field-scale Channel of an Irrigation-dominated Watershed
AU: * Gao, P
EM: pgao@ucdavis.edu
AF: University of California, Davis, Department of Land, Air, and Water Resources, Veihmeyer Hall, One Shields Avenue, University of California, Davis, CA 95616 United States
AB: Sediment entrainment and transport are major water quality problems that require TMDLs for impaired water bodies. In the Salton Sea watershed (southern California) irrigation is the predominate source of runoff and sediment mainly stems from irrigated agricultural fields. It is therefore essential to control sediment release from the fields in order to meet the requirement for sedimentation TMDLs. Unfortunately, the lack of knowledge on soil erosion and sediment movement hinders the development of best management practices at the field scale. To understand the dynamics of suspended sediment transport, a field-scale drain channel connected to six agricultural fields was monitored for 5-minute average sediment concentration during a 3-month crop season. Three individual irrigation events are selected to represent furrow and sprinkle irrigations at the early stage (i.e. stand establishment) and the late stage (i.e. crop growing), which have different effects on sediment transport. Analysis on discharge and sediment concentration hydrographs and the associated hysteresis loops reveals that at the early stage, sediment is supplied from farmlands and partially deposited in and transported out the field-scale drain channel with higher sediment loads for furrow irrigation. At the late stage, sediment is conveyed from both farmlands and the channel bed due to confined soil erosion in the fields and preceding sediment storage in channel. Sediment dynamics are further complicated by concurrent irrigation of multiple events. Two samples of multiple irrigations disclose that sediment transport is not only controlled by hydraulic forces but also by mixing and routing of water and sediment.
DE: 1803 Anthropogenic effects
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1886 Weathering (1625)
DE: 1625 Geomorphology and weathering (1824, 1886)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting