6 JUNE 2012 ESTUARY NEWS delta from the Sacramento River, was north. Typically, Old River is saltier than call the big “noise” of the tides. At the NETWORK answered with the installation of the Middle River at this location, suggesting TECHNOLOGY Jersey Point Station, for example, daily SNAPSHOT first hydro-acoustic meter at Freeport the former carries the lion’s share of the water from the western delta. The 14-day peak tidal flows can be on the order The flow station network developed in 1978. A decade later, water manag- Measuring Flow: The Master Variable of 150,000 cubic feet per second (cfs), ers and scientists wanted to monitor average of the sum of the Old and Middle over time in response to a series of River flows is known as OMR and appears while the net flow may be 2,000 cfs or questions. The first question, how the influence of the export facilities Stand on a tule island at the junc- and federal water managers use flow less. According to Burau, this means on the north-to-south movement of in numerous regulatory documents and much fresh water was flowing into the court cases. tion of two delta channels and you’d station network data to make critical continued to page 8 water from central to south delta. So think you could tell which way the daily decisions about how much fresh they installed two more Sutter-Steamboat Corridor - Sutter water was flowing. Surely anything water they can pump to cities and 122°00' 121°45' 121°30' 121°15' acoustic velocity meters at and Steamboat Sloughs are significant that looks so much like a river natu- farms, and when and where. Wildlife Old River at Bacon Island 80 Sacramento conveyance channels that carry, at times, rally flows downstream, from the hills scientists also use this information and at Middle River (1987). half of the water that passes the city of to the sea? But the Delta is not a to protect fish species endangered by Sacramento In the early 1990s, water Sacramento. Sutter Slough carries the one-way system, nor is nature entirely pumping and loss of habitat. In Cali- River project operators installed bulk of the net flow; Steamboat Slough at the controls. Throw in ocean tides fornia’s long history of wrangles over two stations in the Wal- is much more strongly tidally-affected. 38 30' coming in and out, pumps directing water, many resulting court decisions, ° Delta area nut Grove area, so they The flows in both of these channels are FPT water from here to there, and sea- biological opinions, and water qual- San San Joaquin could find out how much strongly influenced by Sacramento River sonal ups and downs, and the only ity standards have become, to some Francisco Freeport flows and Delta Cross Channel gate opera- River ater water was flowing from people who can really tell which way extent, reliant on the numbers spit out the Sacramento River into tions. Hydrodynamics data gathered from er the water is flowing at any given time by the flow stations. Riv the central Delta through SUT and STM is important in the study of or place aren’t standing on a tule the Delta Cross Channel salmon outmigration. The one number everyone has Ship Channel Sutter/ island. They’re sitting in a dark room and Georgiana Slough, the Yolo Bypass – The flows entering the staring at computer screens showing wanted from these submerged out- Steamboat Sacramento Deep W so-called Delta Transfer posts scattered throughout the delta is delta from the Yolo Bypass are computed the minute-by-minute measurements Elk Slough HoodCorridor Flow. Finally, a combina- the ‘”net flow, or the amount of water as the flow in Cache Slough (CCH), minus of the USGS flow station network. tion of four stations in the the flow in Miner Slough (MIN). The com- flowing in a channel with the tidal flows SUT 5 er south delta were installed putation also measures the tidal and net The network is pretty comprehen- averaged out. In the early days, getting Delta onsumnes Sutt C to estimate delta flow to exchanges into the Liberty Island/Cache sive. Over three decades, and with the this number involved a lot more than a Slough Transfer Slough the export pumps. Below is Slough region, an area slated for sig- help of various state and local agen- few clicks on a key pad. The technology MIN WGA STM Flow a description of the groups nificant restoration efforts. Moreover this cies, USGS has installed 33 stations at to measure the pulse of fresh water Fairfield Creek 38°15' DWS t M of stations used to address region is one of the few places where delta what scientist Jon Burau calls “every moving through a system overwhelmed WGB DCC okelumne y LIB Island Dr specific regional scale smelt are consistently captured. hydro-dynamically significant flow with twice-daily ocean tides simply did Yolo Bypass GEO eamboa questions. CCH t SFM split or confluence” in the landscape not exist before the mid 1970s. Particu- S NFM Mokelumne River System Exchange - Grand of the delta’s 700 miles of channels larly challenging was to try to extract Delta Outflow - The sum Most of the Sacramento River water that is 12 er iv Mokelumne (see map). Most of these stations this number in the 500 meter wide R of the measured flows from exported south of the delta flows through River System R employ a gizmo called a sideward- channels in the delta. RIO yler Island iv stations at Rio Vista (RIO), the Mokelumne River system. When the Rio Vista T er looking acoustic Doppler current pro- Brannan Staten Island Exchange Three Mile Slough (TMS), San Delta Cross Channel gates are open this But that’s exactly what the state’s Lodi filer, mounted on a piling or channel Threemile Slough Island Andrus Joaquin River at Jersey Point region is essentially riverine, but when the Department of Water Resources Is 12 marker. These devices bounce sound Suisun Marsh to Bouloin Is (JPT) and Dutch Slough (DCH) gates are closed, this system is virtually Salinity TMS MOK LPS (DWR) set out to do in the late 1920s. amen are used to estimate delta tidal. The data from the MOK and LPS waves off particles in the water across Control Gate acr DEC Researchers first stretched a cable S Webb San Joaquin outflow. Delta outflow is a key stations may also be relevant to salmon entire river channels, measuring flow, Tract Venice across the channel, called a tag line, Sherm an FAL Is King River/Central outmigration, and critical in monitoring the also called “discharge,” as a volume Island ORS Mandeville Is Is ecosystem metric because it then attached their boat to the cable. PRI system’s response to the proposed resto- per time (such as cubic feet of water 160 JPT Delta Exchanges is a measure of water received As the boat moved through 12-24 MLD Jersey MRC ration of McCormack-Williamson Tract and per second). Small solar panels power Is 99 by San Francisco Bay (i.e. stations along the cable, they used a 4 Colum bia inputs less exports and con- Staten Island. the sensors, and help them relay the Antioch DCH HOL ORQ Cut S 38°00' Bacon an Joaquin device called a Price AA meter to take Old TRN sumptive use). information they collect to computers Is Turner San Joaquin River/Central individual water velocity measure- Cut in operations rooms and science labs OLD Stockton Delta Transfer Flow - The Delta Exchanges- Exchanges of water ments. By summing the flow curves at Delta Outflow Palm MID throughout California. Tract delta transfer flow is comput- from the San Joaquin River into the central each station between tidal peaks, DWR R Middle River Discovery iv M STK ed as the difference between delta are important for understanding how “We happen to have a flowing produced a snapshot of net discharge Bay er iddle Old & the flows measured at sta- system, and it’s flowing not just in one at that time and place. Roberts the salt and sediment fields evolve. The Middle Island tions WGA and WGB, two flow four stations used to calculate this ex- 4 R direction but it’s flowing every which iver R “These were incredibly labor-in- Rivers ORF iv stations located near Walnut change are Turner Cut (TRN), Middle River way, because of tides, and rivers com- Export Flows er tensive, even Herculean, field efforts, KEY VIC ictoria Grove. The calculation helps north of Mildred Island (MRC), Old River ing together, and pumping,” says Anke Flows V working with multiple boats over 24- Clifton Court Canal Union Island water managers estimate north of Frank’s Tract near the conflu- Mueller-Solger, Lead Scientist of the Flow Stations Forebay the amount of Sacramento ence of the San Joaquin and Mokelumne hour periods, but they did an amazingly GLC Grant Line Canal Interagency Ecological Program for River water that flows into Rivers (OSJ) and False River (FAL). These the Delta Stewardship Council. “Un- accurate job given the technology they Station Groups had,” says USGS scientist Jon Burau. State Water Project DMC the central delta through the exchanges strongly influence the rate of derstanding anything in this system These groups draw data Pumping Plant Mokelumne system (the Delta entrainment of salmon outmigrants into must start with a good understanding 132 Eight decades later in the 2010s, from 22 of the 33 individual Central Valley Project Cross Channel and Georgiana the central delta.