Monitoring agricultural nutrient run-off to protect Ebro River

Background

The Ebro is the longest river in Spain culminating in the protected Ebro River Delta wetlands. Agricultural run-offs along the way, particularly nitrates during irrigation season, are threatening river health and can lead to eutrophication. Ebro River Authority wants to monitor the problem to drive remedial action. As a pilot site, a pumped measurement kiosk near Ballobar was selected.

The challenge

Ebro River Authority wanted to find out if extensive irrigation used by farmers during autumn irrigation has an adverse effect on fertiliser run-off into the Ebro River. As a pilot, SWS nitrate sensors were deployed to a pumped measurement kiosk in Ballobar. The client's performance target for the monitoring solution was as follows:

• Accuracy & precision: >90%
• Remote/unattended use
• Service interval: 1 month

The above was run with ADASA Sistemas, a leading water sensor solutions provider, commissioned by Ebro River Authority to independently assess the suitability, usability and readiness of the SWS sensors.

The solution

A SWS DropletSens™ NO3 sensor probe with 20 μm mesh size inlet filter, alongside other physical sensors, was deployed in the measurement kiosk overflow reservoir, to which Ebro River water was pumped. The SWS sensor was installed and calibrated at Day 1 and reagent cartridge and inlet filter changes performed at Day 30 and Day 60. Throughout the 3-months deployment, the sensor was set to autonomously measure nitrate levels in the river water every 10 seconds, with at least weekly switches to an onboard nitrate standard for quality control. Spot samples were also measured in the lab for performance bench marking.

The results

The deployment was successfully completed with the following validated monitoring performance:

• All client targets on accuracy & precision, valid measurements and service interval achieved
• Compatibility with high turbidities up to 250 NTU demonstrated

The high-density, lab-quality data showed significant daily and short-term fluctuations of nitrate levels in the Ebro, but also a clear increase throughout the irrigation season.

• >750,000 measurements points provided by SWS probe
• Nitrate levels started at 30 mg/L in August, rising to >50mg/L end October

The data set will inform the River Authority's discussions with local farmers, aimed at minimising this agricultural run-off.

Following this pilot success, it is planned to extend monitoring to all measurement kiosks and up to 20 measurement locations along the Ebro River.

This was an excellent opportunity to test SouthWestSensor's nitrate sensors in a relevant scenario for our client Ebro River Authority. We found the sensors to measure nitrate levels accurately, whilst being compatible with standard servicing by our field engineers. We are now advancing discussions with Ebro River Authority for further deployment and wider roll-out, to help them to monitor the health of this vital ecosystem and drive protection and remedial action against excess fertiliser run- off.

- Jordi Cros, Innovation Manager, Adasa Sistemas.