The Problem

Water managers, who make the decisions on how water can be used, are getting inaccurate water flow data because the flow of the river is only measured manually every six weeks. The flow changes when debris such as rocks and silt get shifted by the force of the river. Erosion and runoff affect the flow quite a bit and the data changes fast in a short amount of time. These changes make the flow calculations, based off of the previous flow measurements, inaccurate. Hydrologists also sometimes have to drive up to three hours to get to the their sites and then wade across the river to take their measurements, often slipping on muddy banks and algae covered rocks, which can be dangerous. Rivers and streams contain a lot of the water that humans use, but measuring that water has its problems. Accurate measurement is important because those measurements affect decisions that water managers make about how much water people can use and how much needs to be stored to sustain us during dry seasons.

 

 

 

The Solution

Our Quadcopter LiDAR Remote Flow Analyzer can steadily hover near the surface of the river and cover much more area and also enable the survey job to be done quickly and efficiently so that the surveys can occur more frequently.

LiDAR is a radar-like system that uses multiple laser sensors to build a 3D image. When it is over a river it measures bathymetry which is the topography of the bottom of a river. This bathymetry can then be analyzed to calculate the river’s volume. The volume of the water is translated into water flow in cubic feet per second using computer modeling. We still expect that the Acoustic Doppler would need to be used to initially to calibrate the computer models and occasionally to verify them.

Using LiDAR to measure the profile of the riverbed through the surface of the water presents challenges.  These challenges include that traditional LiDAR systems can only penetrate water 4cm deep. Battery power and water refraction also present challenges.  Traditional LiDAR lasers operate in the red spectrum (1064 nm). Our LiDAR system proposes using a blue green laser operating at 532 nm which would have the ability to completely penetrate the water. We would also use the traditional red laser to map the bank’s topography outside of the water as well as the water’s surface.  However blue green lasers come at the cost of higher power requirements.

To address the need for higher power requirements a larger battery will be needed.  We believe current lithium ion battery technology will be powerful enough to run the blue green LiDAR laser and still be light enough for the quadcopter to carry it.

Obtaining bathymetry with LiDAR has one more challenge that we discovered.  When light travels through water it bends and slows the light down. We can compensate for this if we know the LiDAR’s height above the water.  We would use our red LiDAR laser to determine the height of the quadcopter above the river. We could then use the water’s refractive index to compensate for the refraction of the water.

We determined that this is a viable solution that can initially be operated on site by the USGS hydrologists.  If this proves to be successful, in the future, it would be used remotely. Each gaging station could have its own quadcopter LiDAR system housed in a secure “garage”. Remote commands could be sent to the quadcopter using the existing communications path currently used to read the water levels. This would also allow the USGS to make more frequent measurements as well as special request measurements in the event of rain storms or other events that could change the river’s bathymetry.

Innovation

One currently used technology for gauging river flow is the Type AA meter. The Type AA meter is basically a wading rod with a spinning flow meter on it. The rod has a flat bottom and it is used to measure the depth of that particular spot in the river. The flow meter is spun by the water as it pushes by and is used to measure the CFS. This is a simple and inexpensive device, costing around $1400 each. Hydrologists have to wade across the river with the current pushing against their legs. Doing this, they risk slipping on the muddy bank or algae covered rocks. Another downside to this method of measuring is the fact that it can be inaccurate since the Type AA meter just measures the spots in the river where the hydrologist sets it down and flow is only measured at the depth where the flow meter is mounted, not at every depth at that point. We learned that the flow of a river is different throughout because of rocks, bends, furrows, and other different shapes in the riverbed that can change the speed and direction of the water at those points.

Another current measuring device that is being used by the hydrologists is the Acoustic Doppler. This is a device that uses an Acoustic Doppler sensor mounted to a floating frame. The Acoustic Doppler sends out a sound pulse which bounces off particles that are suspended in the water and moving in the current. The Doppler then receives and analyzes the rebounded sound wave which determines the speed of the moving water.  This is the most accurate piece of technology that is currently being used. However, there are some flaws with the device. It is very expensive, with a cost of around $30,000. It also has to be used manually which means the hydrologists have to drive out to each gauging site and wade across the river.

Our solution takes all of the positive aspects of these devices, and it fixes the disadvantages. For example, it is much more affordable than the Doppler. With all of the currently used methods of measuring river flow, the hydrologists have to drive all the way to their measuring site, which can take hours. Our current solution can be stationed at each site and controlled remotely, so the hydrologists can check the flow rate more often without so much time consumed by driving. Another benefit of our solution is that it will reduce the risk of injury to hydrologists who measure the water because a quadcopter can hover over the water and be controlled remotely whereas the Doppler and the Type AA meter require wading across the river. This solution will not only benefit the hydrologists, it will benefit regional water managers who will be able to distribute water more accurately with the right restrictions in place to maintain needed water storage for future droughts while still allowing enough water for agriculture, business, and residential needs.

Solution Development

We use the Engineering Design Process to create and refine our projects. This process includes defining the problem, exploring ideas, concept design, creating a prototype, experimenting, and refinement which leads back to redesign.

PROBLEM: According to local USGS and Division of Water experts, there is never enough data to accurately make the best water management decisions. Not getting measurements often enough when riverbeds are constantly changing and risking injury by wading the river for measurements are their biggest challenges.

EXPLORING IDEAS: We learned about the Acoustic Doppler, since that was the preferred device of our local hydrologists at the USGS.

DESIGN: Our first design was a small rover that would be stationed at gauging stations and drive across the bank and paddle across the river, using the Doppler to measure flow.

PROTOTYPE: We decided to wait to create a prototype until we had gone through enough design cycles to know that we had an idea that was feasible.

EXPERIMENT: When we talked to the USGS about this idea, we learned that the Doppler cost $30,000 dollars, and the garage and rover would have to be much larger than we had first thought. One of the benefits we had thought of was being cost efficient, but this design did not necessarily promote that.

REFINEMENT: We learned about LiDAR and started back into the design stage of the Engineering Design Process. We realized that the rover, although a good idea, could be made better. We will continue to refine the quadcopter design until it is completely feasible or until the idea goes open-source.

We’ve gone through several iterations of the Engineering Design Process and modified our idea each time. The solution we have now is a quadcopter that will hover above the river and shoot a blue-green LiDAR into the river to detect the riverbed while a red LiDAR detects the land and the surface of the water. We have talked to both John Simpson at the Colorado Division of Water and Kevin Murphy at the USGS and made modifications based on their feedback; including learning that we could tie into the communication that they already use to gauge the river height which we can now add to our design concept. Our current prototype is a model with a small quadcopter that moves over a small container of water with particulates inside it that show the lasers that we have attached to the bottom of our quadcopter.

We are continuing to work on learning more about LiDAR and understanding how to mitigate the challenges that our product will encounter with the help of our local professionals at the USGS and Colorado Division of Water. We are also going to learn how all of the different components will need to go together and communicate with each other to get the data, store it safely, and send it back to the hydrologist’s office.

Implementation

The items needed to implement this project include one red LiDAR sensor, one blue-green LiDAR sensor, a Uno Rev3 Arduino microcontroller, and extra battery capacity for extended flight time and for powering the LiDAR system. A DJI Phantom 3 quadcopter will be used to carry the sensors. The DJI has built in GPS navigation system which means we will not need an additional GPS system for tracking and data mapping.

Both weight and cost were considered when evaluating this solution.  The weight of all the components that we will be using is 396.5g, just under the 400g capacity of the quadcopter. The total cost of the components is $809.00.

The most accurate system currently used by hydrologists to measure river flow is the Acoustic Doppler, which costs approximately $30,000. Their other common measuring device, the Type AA meter, costs about $1400. Since our solution is a fairly simple combination of available components, there won’t be significant additional costs associated with implementation. So, we feel our solution is a very cost effective one.

In order to put this solution into action, we will continue to talk with Kevin Murphy, Lead Regional Hydrologist from the USGS and John Simpson, the Assistant Division Engineer for the Colorado Division of Water Resources.  Working with these two professionals and following our Engineering Design Process (EDP) we will further refine our idea and ensure that it is a product that would efficiently do the necessary work. After that, we will talk to engineers about making the proper connections and programming the Arduino to accept the LiDAR input. Data storage will also need to be considered to hold measured data until it can be sent to the hydrologist’s office and confirmed as valid. Our team will then create designs using Fusion 360, a CAD modeling program. We will use the model to create a prototype using 3D printed parts. Once a prototype is established, we will talk to SEOC, a technical business incubator that we have talked with before about manufacturing and marketing issues to consider.      Our initial thoughts are that our product could be marketable to the USGS and Division of Water as well as the Fish and Wildlife Service, irrigation ditch managers, and river recreation companies. We feel that personal contacts and on-site demonstrations will be the best way to make these groups aware of our product. We will also look into open source hardware design licensing so that other innovative people around the world could continue to improve the product and also find other creative uses for it.

We feel that the quadcopter LiDAR system is a feasible project. It is a more cost effective and accurate way to populate water flow tables than what is currently being used. We have received positive feedback from professionals in the industry and we look forward to further developing this product.