Background and Challenge
In recent years, the Coquimbo region has experienced severe water shortages, leading the Chilean government to declare a drought emergency in both 2022 and 2023¹. Climate change has intensified the problem, causing unpredictable rainfall and increased evaporation rates, posing risks to agriculture, drinking water supplies, and local ecosystems.
Traditionally, reservoir monitoring relied on manual measurement methods, which were both time-consuming and prone to inaccuracies. These older methods produced limited data, creating uncertainties in tracking precise water levels, identifying trends, and effectively managing drought and flood risks. To address these issues, the Ministry recognized the need to transition to a more reliable solution, namely SPH Engineering’s UAV-based echo sounder system.
Key Activities and Technology Used
Throughout 2024, the Ministry conducted extensive UAV-based bathymetric surveys on four key reservoirs: Embalse Cogotí, Embalse Puclaro, Embalse Recoleta, and Embalse La Paloma. The project employed a DJI Matrice 300 RTKdrone and DJI D-RTK 2 base station, equipped with the following devices for data collection:
- Photogrammetric cameras provided detailed aerial imagery, which helped to create high-resolution orthomosaics and digital elevation models (DEMs) that accurately represent reservoir and surrounding terrain conditions.
- Operated by SkyHub, the ECT 400 echo sounder provided precise depth measurements synchronized with exact GPS coordinates, greatly improving bathymetric data quality.
- Drone flight paths were planned using UgCS, mission planning software. This ensured thorough coverage of extensive reservoir areas and optimized data collection efficiency.
- Collected data was processed in Hydromagic software, which resulted in highly detailed bathymetric maps and precise water volume calculations.
Results
The UAV-based approach provided reliable and comprehensive data, significantly improving water resource management:
Embalse Cogotí. Initially measured at a critical low of 1.14 million cubic meters in March 2024, Cogotí's water volume significantly increased to 16.46 million cubic meters by July following seasonal rains⁵. This data directly affected critical decisions regarding water distribution for agriculture and municipal usage.
Embalse Puclaro. The April survey measured 9.9 million cubic meters, providing vital data for immediate resource allocation³.
Embalse Recoleta. Initial measurements in February showed 7.1 million cubic meters, rising to 10.04 million cubic meters by July, showcasing seasonal impacts and supporting better awareness².
Embalse La Paloma. Updated volume measurements provided a comparison with historical data from a previous survey. This will help with assessments of long-term reservoir storage trends and sedimentation impacts⁴.
Limitations
Despite significant improvements, several practical challenges emerged during the surveys:
- Lack of Historical Data. Without previous bathymetric data, determining sediment accumulation precisely was difficult, introducing uncertainties in risk evaluation related to reservoir capacities.
- Environmental Conditions. Strong regional winds sometimes delayed UAV operations, making additional planning and flexibility in survey scheduling necessary⁵.
- Operational Limitations. UAV battery life limited flight durations, leading to multiple flights per reservoir. Maintaining accurate GPS signals also required frequent repositioning of base stations, consuming additional operational time.
- Methodological Differences. Slight variations in methods between initial and subsequent surveys slightly complicated direct data comparisons, highlighting the importance of standardized approaches to ensure consistent data quality over time⁶.
Conclusion
Moving forward, the Ministry aims to standardize UAV survey methods, establish historical data baselines for better comparisons, and further streamline the data processing workflow. These steps will help Chile respond more rapidly and reliably to water management challenges, ultimately building resilience in the face of ongoing climate variability and water scarcity.
References
- Informe Batimétrico Embalse Cogotí, Dirección General de Aguas, 2024.
- Informe Batimétrico Embalse Recoleta, Dirección General de Aguas, 2024.
- Informe Batimétrico Embalse Puclaro, Dirección General de Aguas, 2024.
- Informe Batimétrico Embalse La Paloma, Dirección General de Aguas, 2024.
- Segundo Informe Batimétrico Embalse Cogoti, Dirección General de Aguas, 2024.
- Segundo Informe Batimétrico Embalse Recoleta, Dirección General de Aguas, 2024.