Overview

The main goal of this project is to develop a multiscale approach integrating ENS (including NIMS) designs in the observation of a large-scale, dynamic environmental system.  The test bed in this case is the hydrodynamic mixing zone at human-impacted streams and rivers in Southern and Central California.  Specific objectives include:

• To modify the soil pylon hardware making amenable to deployments in river bed sediments (new sensor array referred to as a javelin)
• To demonstrate the sensor javelin in the observation of groundwater-surface water exchanges of nitrate and other species within an impacted riparian zone
• To demonstrate the multiscale ENS approach within an impacted riparian zone over a range of conditions (flows, seasons, etc)
• Collaborate with agency partners and other researchers to create hardware and software architecture conceptual design for ENS and NIMS deployments at local, watershed, and regional/basin scales.

Approach

This project focuses on developing and demonstrating the CENS multiscale ENS approach at two relevant cases: (1) elucidating spatiotemporal variations in biologically significant stream properties in Medea Creek, a small urban stream in Southern California, and (2) using high resolution synoptic sampling of steady velocity and water quality distributions across the San Joaquin River, an agricultural drainage-impacted river in Central California.  The San Joaquin River basin, for example, is already equipped with synoptically sparse, networked gauging stations (separated by 10s of km) which provide time series data on river stage, flow, salinity and temperature data in an existing CI framework called the California Data Exchange Center.  These data enable simple river network routing model calibration and basic flow and water quality forecasting in the confluence zone.  For example, we can predict how a sudden decrease in flow by reservoir operators can be accompanied by an increase in nitrate, salinity, and/or temp in the river if nonpoint source pollution inputs remain reasonably steady.  However, this forecasting capability is not adequate to say whether the water quality changes across the confluence zone will impact salmon migration. But the low resolution knowledge has proven to greatly inform mobile (e.g., kayak-deployed) and higher resolution stationary (river javelin) sensor deployments enabling more detailed characterization of the confluence zone and identification of optimal locations for NIMS RD super-resolution efforts.  Optimal NIMS RD timing is then identified using the ensemble of networked sensors and simulators.

Systems/Experiments

NIMS RD was deployed at a small creek and a moderately large river to test its performance over a wide range of physical conditions.  The first deployment was carried out at Medea Creek in Los Angeles County, CA, a small headwater stream in the Malibu Creek Watershed.  A second deployment was executed over a 55m span across the San Joaquin River, just below its confluence with the Merced River in Central California.  This site was selected because it provided a challenge for the NIMS RD at a larger scale, and because it afforded an opportunity to develop detailed observations of the hydrodynamic mixing in the confluence zone.  Flow in the San Joaquin River is dominated by agricultural and managed wetland drainage in the late fall.  Its flow tends to diminish while increasing in temperature and salinity at this time of the year.  The Merced River, in contrast, is relatively cold and less saline as it enters San Joaquin.   The two rivers had comparable flows at the time of the deployment (October 6-7, 2005), resulting in a visually distinct mixing zone roughly midway across the confluence zone. 

 

In both deployments, the NIMS RD carried a multi-parameter water quality sonde (Hach Environmental, MiniSonde 4a) equipped with temperature, conductivity (specific conductance, SC), nitrate, ammonium and pH sensors.  For the San Joaquin River deployment an acoustic Doppler velocity sensor (Sontek Triton ADV) was also suspended from the NIMS RD unit at the same level and just upstream of the water quality sonde.  Both the Medea Creek and San Joaquin River NIMS RD scans yielded cross-sectional hydraulic and SC distributions at resolutions that would be difficult, if not impossible, to obtain manually.  The resulting monthly 24-hour scans at Medea Creek revealed previously unobserved spatiotemporal stream constituent patterns.  For a given constituent, discernable, interrelated spatiotemporal patterns on several scales were observed.  We focus on electrical conductivity (SC) and temperature (T) to illustrate these patterns and relationships.  T and SC showed varying cross-sectional patterns throughout the 24-hour scan (examples in Figure 1).

Figure 1. Typical cross-sectional (a) temperature and (b) specific conductance distributions produced during 24-h NIMS RD scans of Media Creek for Jul (top), Aug (mid), Sept (bot) 2005 (plot aspect ratio is 1:1).

 

The San Joaquin River low and high resolution velocity fields are plotted in Figure 2.  As the contouring indicates, the low resolution field is characterized by some unrealistic patterns, while the higher granularity sampling effort seems to result in more natural patterns.  Summary statistics for the two velocity fields are significantly different.  The low resolution velocity scan resulted in maximum and mean velocities of 56.3 and 21.0 (SD 23.8) cm/s, respectively; the corresponding high resolution results are 60.6 and 36.4 (SD 19.2) cm/s for the Oct 6 scan, and 58.3 and 37.8 (SD 19.3) for the Oct 7 scan.  The US Bureau of Reclamation Newman gauging station roughly 100 m downstream from the NIMS RD cross-section indicated flow rates of 18.29 and 19.17 m3/s, respectively (average values based on stage at the times of deployment).  The total volumetric flow rate estimated by equation (1) for the low resolution scan was just 4.1% below this value (17.54 m3/s), and the high resolution velocity distributions yielded a flows nearly the same as the gauging station values (18.38 m3/s for Oct 6; 19.33 m3/s for Oct 7). 

Figure 2. Low resolution (10/6/05 top) and high resolution (10/6/05 middle, 10/7/05 bottom) cross-sectional acoustic Doppler velocity (ADV) distributions generated during the San Joaquin River NIMS RD deployment (note: plot aspect ratio is 10:1).

High resolution SC scans for the San Joaquin River cross-section for Oct 6 and 7 are plotted in Figure 3.  The maximum and mean SC values for the first scan were 1291 and 801 (SD 395) mS/cm, respectively; for the second scan these values were 1244 and 765 (SD 373) mS/cm.  Given the lack of significant flow variation over this two-day period, the consistency of the SC distribution suggests that salinity inputs were relatively unchanged over the two-day period, and that the NIMS RD results are reproducible under steady flow conditions.  It is worth noting that this point is true in spite of system dismantling and reassembly between the first and second scan (for security).

Figure 3. High resolution (10/6/05 top, 10/7/05 bottom) cross-sectional specific conductivity (SC) distributions generated during the San Joaquin River NIMS RD deployment (note: plot aspect ratio is 10:1).

Future Directions

The overall theme for future directions in Contam will be scaled-up deployments and integration of multi-hop stationary networks with NIMS and human-actuated sensors. The following are expected milestones in the next year of research:

• Stabilizing the soil pylon and sediment javelin platforms in terms of sensors suites, error and fault analysis
• Expanding the Palmdale from 4 pylons to 12-15 pylons encompassing the 30-acre test site and using data assimilation software upon its completion to explore data and application integrity in the context of the soil pollution prevention problem
• Deploying a stationary javelin network in the San Joaquin-Merced River application which will interact with human-actuated and NIMS RD-mounted sensor arrays
• Make the Contam technology portable to relevant observatory science planning and design efforts (NEON, CUAHSI, CLEANER)