Mapping Hidden Channels with Genesis Live

River channel thalwegs (the line of lowest elevation within a valley or watercourse) are often dynamic, and sometimes hidden features of large river systems.  Especially low slope or impounded systems.  The thalweg is a critical geomorphological feature of river and reservoir systems and affects everything from sediment transport, to fisheries habitat, to algae or invasive plant control.

Thus a good bathymetric contour map is a necessary pre-requisite for effective river and reservoir management.  Here, we walk you through how to use new real time technologies (C-MAP’s Genesis Live) to produce smooth, precise, and accurate maps of hidden river thalwegs all within one trip to the site and with automated post-processing with BioBase’s EcoSound.  We’ll use an annotated image gallery to take you through this process.

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Consumer Sonar for Bottom Mapping: Updated Reference List

Another FAQ we get is wondering if there are published studies using BioBase technology? There are many legacy applications on which the BioBase technology is based. Further, now that a sufficient passage of years has accumulated to support the “research to publication” cycle, we’re happy to share several BioBase-specific studies published in the peer-reviewed literature.  This is far from an exhaustive list and we’ve intentionally left out the niche growth in consumer side-scan technology for creating habitat maps.  If there are good published papers you know of that are not on this list, please share in the comments.

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BioBase Project Propels Jeff Schuckman to Nebraska Game and Parks Employee of the Year!

Lake Yankton, a 332-acre backwater lake on the Nebraska/South Dakota border had a problem. In the summer of 2011, the Missouri River flooded, spilling into the lake a number of undesirable invasive rough fish, including large numbers of carp (silver, bighead, grass, and common), smallmouth buffalo, and gizzard shad. Notorious for stirring up lake bottoms while feeding and spawning — and for overeating zooplankton and aquatic plants — these species degrade water quality and fisheries.  

Overrun by these invasive species, Lake Yankton soon looked like chocolate milk, with a water clarity of only three inches — that’s right, inches, not feet.  So the cavalry was called in to assess the situation and provide a solution. Leading the effort was Nebraska Game and Parks Commission District Fisheries Manager Jeff Schuckman.

Fortunately for Nebraska anglers, this wasn’t Schuckman’s first rodeo. He knew the lake could be rehabilitated with careful application of Rotenone, a common fish-killing chemical. The challenge would be to determine just how much of the chemical was needed, and then purchase and apply just enough to do the job — no more, no less.

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BioBase 3 Step Process: Important Details!

A primary strength of BioBase EcoSound is its simplicity and that is reflected in the easy 3 step process of “Collect,” “Upload,” and “Analyze” (Figure 1).

Figure 1. The core process of EcoSound depicting the 3 Steps of “Collect,” “Upload,” and “Analyze.”

But there are many strategies that users can employ that will ensure that they will get the best EcoSound outputs possible.  We’ll focus on several questions under each of the three categories

COLLECT

What is collected?
BioBase EcoSound analyzes the downlooking 200 kHz broadband frequency from any Lowrance, Simrad, or B&G sonar/gps chartplotter capable of recording files as .slg, .sl2, or .sl3 to high capacity storage media (e.g., SD, MicroSD).  Each of the 10-20 acoustic signals per second has detailed information about the depth (depth to the top of the substrate), bottom hardness, and the height of aquatic vegetation canopies if present.

How do you collect data?
After you open your BioBase account, go to the Support and Resources page and print off the quick start guide for your unit (Note: Elite Ti users should reference the HDS quick start guide).  These guides gives you important instructions about setting configurations and how to record your data.

Choose the hardware, watercraft, and mount that will best suit your needs.  You will get the most consistent and clearest signal from a fixed transducer mount either on the transom or through the transducer hull.  Take careful measure to ensure the proper transducer angle and to minimize the creation of cavitation (air bubbles) near the transducer face.  Your unit will come with a detailed transducer installation guide – read it and follow it carefully!  Cavitation can create false vegetation detects or missed bottom detects and greatly affect the speed at which you are able to map.  Click here to learn more about transducer selection and installation.

Once you have a good understanding of how to mount your transducer, you have a range of portable options available if you need to either get into small water bodies or transfer the equipment to multiple vessels.  This post has a great gallery of photos from the BioBase mapping community demonstrating a range of portable options.   With any mount, ensure that the GPS position is very near the transducer such that X,Y, and Z positions are all aligned.  For console-steer boats, consider a Point-1 GPS external antenna.  Learn more about GPS here.

How far apart do I space my transects?
Using geostatistics, EcoSound creates bathymetric, aquatic vegetation, and bottom hardness digital models with point data much like how land topography is mapped (e.g., “Digital Elevation Models” or DEM’s; Figure 2)

Figure 2.  Schematic simulating the actual bottom area quantified by a 20-deg Lowrance Transducer (model HST-WSBL – white box) and 6-deg Airmar Transducer (model TM-260 yellow box).  At 5 ft, the 20-deg transducer insonifies a 1.76 ft area, whereas the 6-deg insonifies only a 0.5 ft area,  Given the rapid ping rates, most applications will have very high overlap of adjacent pings and thus be quantifying the entire bottom directly under the mapping vessel.

Once you understand where actual measurements are being recorded, you can make an informed judgement on the appropriate level of bottom “sampling” with transects.  As with any kind of sampling, the appropriate level of sampling depends greatly on the study or management objectives. Users might be able to use painting as a useful analogy for a starting place to guide transect spacing decisions.  For instance, if you are painting a large flat wall, you use a large roller and your objective is to get the best coverage as fast as possible.  Similarly, if you are mapping a large lake or bay with gently changing bottom features, you can space transects relatively wide (e.g., 100-300 m) and drive a modest speed (e.g., 8 mph or 12 km/h) if you have a good install with your transducer.  In contrast, if you are painting an ornate cabinet with detailed carvings, then you have to use a small brush and spend a lot of time getting that small brush into all cracks and crevices.  Same goes with a highly complex lake or reef bottom.  In these cases, close transects (e.g., 5-m) with a narrow beam transducer, and slow speed (2 mph or 3 km/h) might be called for.  Our Transect Design Blog goes into these issues in more detail.

Log Sonar while doing other activities
Running BioBase EcoSound surveys does not need to be a dedicated activity that you now have to layer onto your other obligations.  Rather, EcoSound is a tool for passive data capture during activities you are already on the lake conducting.  For instance, biologists are on lakes and bays everyday throughout the globe bouncing spot to spot taking samples of aquatic plants.  Most have a gps and sonar on their boat to find where they are going.  EcoSound allows them to be recording and capturing detailed spatial information about exactly how much plants are growing not only at their sampling spot, but between sampling location.  Many Aquatic Plant Biologists using EcoSound for the first time are shocked by what they missed with their original surveys.  This analysis provides possibly the most eye opening example of how spatially dynamic aquatic plant growth is in glacial lakes.

The second example is sampling fish with electrofishing.  Habitat degradation is often cited as one of the primary causes of global fisheries declines, yet rarely are habitat data collected in conjunction with fisheries data.  Recently, Lowrance and BioBase teamed up with the global leader in Electrofishing Smith-Root to demonstrate how Fisheries biologist can integrate Lowrance HDS into their electrofishing boat and collect important fish habitat data while electrofishing (Figure 3).  BioBase EcoSound allows you to simultaneously collect both fish and habitat data, thus leading to better informed Fisheries Management decisions.  Read more about this partnership here.

Figure 3. Integrate Lowrance HDS into your Electrofishing Boat to monitor boat function, view structure real-time, and record important fish habitat data.  Inquire with Smith-Root about how to retrofit old boats or outfit new ones.

UPLOAD

Cloud-computing has quickly become the new standard for managing large datasets.  Remote servers and databases are better able to manage the large data-rich .sl2 files than most desktop programs and external storage media.  Use our desktop upload tool to select your .sl2 file from your card and upload.  After your upload is complete, the file hits one of our dozens of servers that goes to work analyzing every signal.  Our algorithms perform many automated tasks including:

Data Cleansing
Signal quality is reviewed for every signal.  Those not passing certain tests, are discarded (at 10-20 data points per second, you can afford to discard some bad ones).  These tests include whether the operator was going too fast (e.g., 20 mph for depth, 12 mph for vegetation, 10 mph for composition), whether the signal was too noisy, or whether depth was lost for some reason.  Bad soundings are removed automatically.

Feature Extraction
With 10-20 data points per second, aggregation is necessary to create manageable outputs that aren’t “too busy.”  Therefore, EcoSound algorithms create georeferenced data “points” that represent averaged areas (see Figure 2).  These X,Y,Z points can be exported from BioBase and imported into GIS for important exploratory analyses (e.g., to understand data coverage and spacing of attribute points) or statistical analysis (e.g., statistics from transect studies).  Most other hydroacoustic processing software stops here.  BioBase takes it one step further and creates robust geostatistical maps.

Geostatistical Interpolation
Finally, once the coordinate points are created for all layers, the points are sent to a generic kriging algorithm that uses geostatistical models to make predictions of depth, vegetation, and bottom hardness in areas not sampled.  Kriging creates a uniform grid (grid cell size is user configured and 5 times less than the track buffer) for each EcoSound layer.  Redundant point data while idling gets averaged into one grid cell value.  By knowing the value of neighbor points, kriging can predict the value in an unsampled location.  Read more here…

Quality Control with Real People!
Although automation has led to huge productivity gains in the last century, quality control by humans is a critical component to a full solution.  Accordingly, BioBase Quality Control Engineer staff review every uploaded sonar log and review the quality.  Staff ensure the signal looks clear, that the output is free of evidence of improper installation (e.g., slanted transducer, Figure 4), and that the digital shoreline (lake polygon shapefile) aligns with the Bing aerial imagery and has sufficient zero values along shore such that contours do not intersect shore.  In general, QC staff will review your trip and make adjustments to sensitivity or shorelines within 24 business hours of your upload.  Maps should be considered “provisional” prior to QC review.  After QC staff check off, users can do their own QC checks prior to analyzing the map data in depth.

Figure 4.  Sample output with a improperly installed transducer that would be flagged by BioBase’s Quality Control Team.  QC Staff check every file and will alert you to verify the output and possibly make corrections.

ANALYZE

Trip Replay
After you receive an email informing you that your trip is ready for viewing and QC have completed their review, you can replay your sonar log synced with your track and interpolated map and accompanying data.  You can add or delete data by clicking on areas on the map, on the sonar log, or in the data table below the map and choosing delete.

Polygon Tool
Digitize an area of interest such as a bed of an invasive aquatic plant species.  The EcoSound polygon tool will use the polygon like a cookie-cutter and clip the statistics for just your specific area.  Further, BioBase has a partnership with United Phosphorus Inc. to help aquatic plant managers create precise herbicide treatments with their polygons using the UPI Treatment Tool. Finally, these polygons can be exported as shapefiles and converted to .gpx for viewing on your Lowrance Chartplotter.  This feature enhances precision of aquatic plant management and dredging activities.


Data Offset
Gain accuracy in water elevations by using the offset tool to correct for your transducer depth or create a map with a benchmark elevation as discussed in this blog.  If you are working in a coastal area with tide stations, your trip will be automatically offset to Mean Lower Low Water (MLLW) every 5 minutes as described here.

Trip Reprocessing
If you make edits to your map or want to fill in gaps in your map with a buffer, you’ll need to send the trip back to the BioBase servers to update the map and datasets.  You can increase map detail by decreasing the buffer, with a minimum buffer of 5-m and 1-m grid cell resolution.  You can fill in gaps and create a generalized map by increasing the buffer.

Merge Trips
With multiple-use subscriptions or special single-lake subscriptions, you can combine files from anyone using a Lowrance HDS or Elite HDI/Chirp to slowly build the best map ever created.  One amazing example is the effort put forth by citizens on Ten Mile Lake in Northern Minnesota simply by passively recording their sonar while they were out boating or fishing during a 2 year span.  Most commonly, BioBase users use the merge function to combine multiple smaller sized files into a larger aggregate for an entire waterbody.

Export Data
The primary strength of BioBase is its ability to rapidly process very large raw datasets and produce valuable spatial data.  As we’ve discussed, BioBase has many “turn-key” features that are valuable to the everyday practitioner who may not be trained in Geographic Information Systems (GIS).  However, the value of BioBase outputs increase dramatically for those who export BioBase data and run spatial analyses or create custom map layouts with BioBase and other data layers.  As ESRI Silver Partners, we support use of BioBase data layers in ESRI products like ArcMap and actually have step-by-step tutorials that will walk you through how to create GIS data layers from your BioBase outputs

Automated Reports

Another popular feature of BioBase EcoSound is that automated summary reports are produced with every upload or merge and stored on a dedicated file server for sharing with partners.  Partners just see the report and do not have access to your account.  Further, if you add waypoints to your map, they can also be shared.  For example, if I want to include a BioBase aquatic vegetation summary report in a larger .pdf report that I am sending to a client or study sponsor, I just include the link in the report and now the person with whom I am sharing has dynamic html with which they can interact and find the statistic(s) that most interest them.

These reports have many numbers and might be confusing at first, but simply hover over the question mark with your mouse, and it will tell you what the numbers mean.  Data summaries are created from the “point” data along your track and also the kriging interpolated “grid” data that is created from the point data.  If you are primarily interest in monitoring repeated transects or the max depth of vegetation growth, use the point data statistics.  If you are doing back and forth mapping (most EcoSound applications), use the grid statistics.

COLLECT – UPLOAD – ANALYZE!

CHIRP from a bottom mapping perspective

Maybe you’ve been hearing about this term in sonar circles called “Chirp” and noticing that most consumer sonar units now come with Chirp capability. Indeed, Chirp is a game changer for more precise definition of acoustic targets suspended from bottom (e.g., fish) and the technology is helping more anglers find fish in a wide range of aquatic environments (Figure 1).  But what does Chirp mean for mapping the bottom of waterbodies?  Does it provide any advantages or disadvantages over traditional 200 kHz frequency broadband sonar that is the foundation of Insight Genesis and BioBase
EcoSound mapping services?  Here we take a brief look at Chirp, explain what it is, and present some findings from preliminary tests in a couple of different lake environments.

Figure 1. Sample sonar screen grab from a Lowrance HDS Gen3 running high Chirp frequencies over numerous fish targets.

Compressed High Intensity Radar Pulse
Acoustic target separation is often tied to the pulse length or duration.  Longer pulses give better depth penetration, but less target separation.  For suspended targets, Chirp represents the best of both worlds by sweeping many short pulses of a range of frequencies within a relative long pulse burst.  Three Chirp ranges (Low 40-60 kHz; Medium 85-145 kHz; and High 130-210 kHz) typically accommodate most situations for locating fish targets throughout a range of depths.

Chirp Performance For Tracking Bottom in a Range of Conditions
It has been well established in recreational marine circles that Chirp is a benefit to mapping suspended targets, however differences in how bottom is declared with Chirp vs the traditional single 200 khz frequency (for which BioBase EcoSound and Insight Genesis was developed) is a question for which we recently sought an answer.

Tracking Bottom in Dense Submersed Aquatic Vegetation
Tests were conducted in Gray’s Bay of Lake Minnetonka in August 2014.  Repeated transects were run over a dense bed of submersed vegetation with a Lowrance Elite 7 Chirp, and HDS Gen2 with a Chirp compatible SonarHub running both traditional 200 kHz and High Chirp frequencies.  Below is a plot showing the EcoSound depths from both the 200 kHz and High Chirp Frequencies (Figure 2).

Depth was significantly greater and was closer to truth based on sonar log verification with the traditional 200 kHz frequency than High Chirp.  However, the actual difference in depth declarations between the frequencies was only 6 inches on average.  Plant canopies apparently more quickly extinguish the Chirp signal than the 200 kHz.  Based on these findings and other tests, the 200 kHz frequency remains the recommended frequency for mapping aquatic plant dominated bottoms.

Figure 2.  Average depth declaration by BioBase over repeated transects in dense submersed vegetation (avg plant height of 3 ft) running both Chirp and 200 kHz frequencies.

Bottom Declarations Over Soft Bottoms
Frequently, we get questions regarding whether EcoSound can determine the depth of sediment.  The answer is yes, but only if the “true” bottom is known (e.g., “as built” bathymetry in a human-engineered system) or a desired bottom can be modeled (e.g. how deep does it need to be for waterway management objectives).  If a true bottom can be described, then Lowrance and EcoSound should tell you the precise depth where the water meets sediment.  Simple subtraction of map layers in ArcGIS with Spatial or 3D Analyst (Raster Calculator) will produce detailed sediment maps like produced by the Central Arizona Project.  A question that piqued our interests however, was the difference between 200 kHz and Chirp bottom declarations in relatively soft bottoms.  Because the Chirp signal appears to attenuate more quickly than 200 kHz, could Chirp be a solution for more precisely mapping the depth of the sediment water interface in softer, plant free bottoms?

The St. Johns River Water Management District at Lake Apopka FL helped address this question by sharing Chirp and 200 kHz frequency sonar logs over bare soft bottoms on Lakes Apopka and Griffen in Florida, USA.  Analysis of approximately 100 data points across both frequencies found almost no differences overall and deviated only one to three inches from true bottom determined from the sonar log (Figure 3).

Although the vast majority of user sonar logs have bottoms that are clearly defined visually and acoustically, there are some bottoms that are so soft and unconsolidated that they are source of philosophical discussions of where the “bottom” actually is.  Further research and testing is needed to determine whether Chirp can be a unique solution for better depth tracking in these and other special use cases where bottoms are highly flocculent.  The more rapid attenuation of the Chirp signal than the 200 kHz frequency in plant bottoms (which may present a similar acoustic signature to a soft bottom) suggests it could be a solution in a narrow range of use cases where the 200 kHz channel penetrates too far into the bottom.

Figure 3. Bottom depth declarations (solid line) with Chirp (Top) and 200 kHz (Bottom) over a soft bottom on Lake Apopka, Florida USA.  Although in this case, Chirp produced a slightly shallower depth (8.0 ft) than 200 kHz (8.7 ft), overall we found very small differences between frequencies in depths over moderately soft, plant-free bottoms.

Conclusion: Use 200 kHz for Mapping
EcoSound and Insight Genesis mapping algorithms were developed and optimized for the 200 kHz frequency.  Over plant-free bottoms, both 200 kHz and High Chirp should perform similarly and precisely map the sediment-open water interface.  However, in bottoms dominated by submerged vegetation, the 200 kHz frequency will produce the best depth declarations and clearest delineation of the vegetation-sediment interface.

Virtual Eyes to See Aquatic Resources in 3D

One of the biggest challenges to understanding aquatic resources are the optical properties of water and an inability of our human eyes to see the complex world that lurks beneath the surface.  In contrast, when “aeroplanes” (that’s what they were called in the Wright Brother’s days) first took flight in the early 1900’s and pilots figured out how to fix cameras to the belly to take aerial photos, it opened up a new world of exploration for biologists and foresters studying terrestrial landscapes.  The term “landscape” got a whole new meaning.

Needless to say, aquatic resource managers and researchers have lagged behind our landlubber counterparts in understanding how aquatic organisms relate to “aquascapes.”  Fisheries biologists have long dropped their nets into an abyss and magically, fish appeared when they pulled them up the next day.  Or, a rake/grapple thrown from a boat at a handful of transects or sampling points was the extent of the sophistication that biologists used to characterize plant growth in the littoral zone of lakes.  Biologists and researchers through the years have grown quite skilled at developing fancy statistical models to make sense of these messy, imprecise data.

Technology is now cleaning up the messiness of aquatic resource data and bringing in a new level of intuitive sophistication and precision.  Advancements in consumer sonar like Lowrance HDS with StructureScan give the researcher an ultra-sound-like picture of the environment they are studying in a small, rugged, and affordable package.

DownScan, StructureScan, Down Scan, Structure Scan Lowrance, ciBioBase
DownScan Imagery of small sunfish hovering over Eurasian watermilfoil plants in Prior Lake, MN as viewed in the ciBioBase Trip Viewer
Lowrance, StructureScan, Side-scan
Side-scan image of boulders, gravel, and sand from a river in Pointe Au Baril, Ontario Canada from a Lowrance HDS8 Gen 2 LSS-1 Transducer.  For a large image library of other impressive StructureScan Images, just go to Google Image and type in “Lowrance StructureScan”

Advancements in cloud computing via ciBioBase has enabled your 8-yr old laptop to do super computer processing tasks and you don’t need a hard drive the size of a closet to store your data. Centralization and automation of industry-standard acoustic data processing tasks creates visually intuitive maps and spatial datasets that are uniform across data collectors and geographical areas.  And, to top it off, your maps are often finished processing quicker than it takes you to make a pot of coffee after returning from the field.

Finally, third party spatial analysis and visualization platforms like those powered by ESRI (e.g., ArcGIS and associated plug-ins, ArcScene, etc) can take your BioBase datasets to the next level by opening up a wide range of advanced analysis and visualization tools.  For instance in the two embedded videos, we demonstrate two outputs derived from the Lowrance HDS -> ciBioBase -> GIS chain of analysis that give the aquatic researcher/manager a birds-eye view of the environment they are managing.  GIS for the aquatic researcher is now more than putting dots on a map.  Time to play some catch up…

YouTube demo of ESRI ArcScene Fly Through of the North Umpqua River upstream to Lake Lemolo in West Central Oregon.  Digital Elevation Data were obtained from the USGS National Map Viewer and Lemolo Bathymetric data were collected with Lowrance HDS by Joe Eilers, MaxDepth Aquatics Inc. Bend, OR and processed through ciBioBase.

ESRI’s ArcScene is used to create a 3D view of a kelp forest mapped with  Lowrance HDS by Rick Ware Coastal Resources Management Inc., Corona Del Mar, CA.  Date were processed with ciBioBase, exported, and then brought into ArcScene.


Amendment to ciBioBase Guest Blog: GIS Tools helping CAP manage sedimentation

Earlier this year, Senior Biologist Scott Bryan from the Central Arizona Project (CAP) blogged about how the CAP is using ciBioBase to manage sedimentation in Arizona’s lifeblood 336-mile aqueduct.  Since then, CAP GIS Wizard Glenn Emanuel has worked some amazing magic on the ciBioBase grid exports using Spatial and 3D Analyst Extensions for ArcGIS (Figure 1).

Central Arizona Project, sedimentation, Lowrance, ciBioBase, BioBase, sonar, mapping, acoustics
Figure 1. Images showing the change in sediment volume prior to and after experimental dredging activities in a Forebay of the CAP canal.  The Raster Calculator in ArcGIS’s Spatial Analyst was used to subtract a “current” bathymetry from a baseline bathymetry (e.g., “as built”) to estimate sediment height and volume.  Images are 3-dimensionally enhanced using 3D Analyst for ArcGIS. Image courtesy of Scott Bryan and Glenn Emanuel, Central Arizona Project

The data and images allow CAP to make informed decisions regarding the efficiency of sediment removal operations.  In addition, ArcScene was used to produce a 3D scene of the forebay (Figure 2), which can then be animated with a video fly-through.

Central Arizona Project, sedimentation, ciBioBase, ArcScene, Lowrance, BioBase, sonar, mapping, acoustics
Figure 2. “Fly-through” images of sediment height  in Little Harquahala Forebay in the CAP Canal collected by Lowrance HDS sonar and GPS, ciBioBase cloud processing software, and finally exported/imported into ArcScene.  Image courtesy of Scott Bryan and Glenn Emanuel, Central Arizona Project.

Any user of ciBioBase properly equipped with the proper third party GIS software can create these amazing map products that are more than just pretty pictures.  They create a real-life, tangible perspective of aquatic resource conditions that ciBioBase users are interested in managing, protecting, and restoring.

CI In the News (St. Cloud Times): Harmful species to hot spots: Technology helps all

Recent feature by Kevin Allenspach from the St. Cloud Times describing how Clarke and lakeshore owner citizen scientists are integrating ciBioBase to better inform aquatic plant monitoring and management in Central Minnesota.

You can read the story here.  Let us help you make your own news (we have lots of ideas)!

ciBioBase Vegetation Mapping

We love to show off the accuracy of our submerged vegetation mapping algorithm.  Check out this break in the weeds that was picked up and clearly displayed in the ciBioBase vegetation layer:

The BioBase vegetation layer is automatically generated by powerful cloud computers so you receive an objective output every time.  The white line on the right and red dot on the left show the boat position as a cross section and aerial view of the water column respectively. 

Submerged vegetation is displayed as percent biovolume (BV%) which represents the percent of the water column occupied by plants.  This provides a clear picture of total plant abundance from each trip on the water.  Data can be passively logged because none of our users have to do any of the processing when they get back to the office.  Do what you were already planning to do and our automated system will take care of the rest.

Let us know if you have any questions about how this process works!

Guest Blog: Using BioBase to determine sedimentation in the Central Arizona Project canal

by Scott Bryan

The Central Arizona Project (CAP) is a multipurpose water resource development and management project that provides irrigation, municipal and industrial water to much of Arizona.  The primary means of water conveyance is a 336-mile concrete-lined aqueduct that transports water from the Colorado River, on Arizona’s western border, across the State to Phoenix, and then southward to the aqueduct terminus near Tucson.  Each year, over 1.5 million acre-feet of water is delivered to our customers.

Since its completion in 1993, the aqueduct system has experienced increasingly severe sedimentation that creates problems within the pumping plants and in the aqueduct itself.  Because the sediments can decrease the flow capacity of the aqueduct, cause damage to pumps and internal systems, and restrict flow through critical filtration units, it is imperative that dredging operations occur periodically.

sedimentation, ciBioBase, water volume, depth, mapping, bathymetry
CAP forebay dredging in 2009

In the past, CAP performed intensive sonar based sediment studies to determine bathymetry and the amount of deposition in the forebay of each of the 13 pumping plants.  The surveys show when and where dredging operations should occur.  These surveys were contracted to outside companies with costs ranging from $40,000 to $120,000 annually.

In 2012, CAP began to use the sonar technology provided by BioBase to conduct its own bathymetry surveys in the pumping plant forebays.  Water depths are compared to historical baseline surveys and the volume of sediment in each forebay can easily be calculated.  Annual surveys allow us to compare sedimentation from year-to-year to determine loading rates and critical areas to target sediment removal.  Surveys of all 13 forebays can now be accomplished in three days rather than six months, and when compared to the expensive surveys from the past, are equally as accurate.

ciBioBase, bathymetry, water volume, depth, Lowrance, acoustics, mapping, sonar, sedimentation, dredging
Blue-scale bathymetric map of a CAP forebay.  The light blue contours show an area that is extremely shallow and is in need of sediment removal.

 

ciBioBase, sedimentation, Lowrance, downscan, sonar, mapping, bathymetry, depth, water volume
Example transect design and resultant bathymetric map coupled with the sonar log viewer.  Notice the detailed image of the forebay’s trash racks produced by Lowrance HDS DownScan
This new approach to bathymetric and sedimentation mapping saves time and money, allows us to evaluate results immediately, and makes dredging operations more efficient and timely.

Scott Bryan is the Senior Biologist for Central Arizona Project (CAP).  After receiving an M.S. in Fisheries Management at South Dakota State University, Scott worked as a research biologist for Arizona Game and Fish for 10 years, then specialized in lake and stream management for seven years at a private consulting firm in Albuquerque.  Scott’s current position at CAP includes a broad scope of work, including aquatic and terrestrial vegetation control, fisheries and wildlife management, invasive species research, and water quality monitoring.