Proposal · Irrigation & CAD Department, Government of Telangana
Drone-based bathymetric survey and siltation monitoring
Reservoir capacity that is measured rather than assumed — proposed as a focused pilot on two to three reservoirs over eight weeks, before any statewide commitment.
Why it matters
- Average gross storage lost to siltation across major and medium projects
- 25–30%
- Storage lost at Nizamsagar, the worst-hit reservoir in the state
- 60%
- Proposed pilot, from planning to reservoir-specific final reports
- 8 weeks
Sources: CWC / SANDRP assessment; CWC Compendium on Sedimentation of Reservoirs, 2020.
The problem
Reservoirs silt up, and storage capacity falls with them. Across Telangana’s major and medium irrigation projects an average of 25–30% of gross storage capacity has already been lost, and at Nizamsagar the figure reaches 60%.
Conventional resurveys mean boats, dive teams and weeks of field mobilisation per reservoir, so they are done rarely. Without current Elevation–Area–Capacity data, irrigation planning runs on assumptions instead of measurements.
The proposed system
One integrated set of instruments, chosen for the conditions in Telangana’s reservoirs.
Drone-mounted echosounder
The principal instrument for deep and turbid water — single-beam, dual-frequency or multibeam.
Green-laser bathymetry
Used selectively in shallow margins, draw-down zones and tail areas. It supplements the echosounder rather than replacing it.
RTK/PPK positioning and GIS
Survey-grade positioning feeding directly into GIS-based capacity models.
Digital capacity database
A living baseline for every surveyed reservoir, updated after each future survey.
What the equipment can do
The programme uses drone-integrated hydrographic systems of a class already in service for reservoir, river and harbour survey work. Typical published capability for such systems:
- Depth range: 0.15 m to roughly 200 m, depending on the acoustic frequency fitted
- Depth accuracy: 0.2% of the measured depth, with millimetre range resolution
- Sounder options: single-beam, dual-frequency, or multibeam for full bed coverage
- Airframe: commercial survey multirotors carrying a 1.3–2.5 kg sensor package
- Positioning: RTK/PPK, with a radar altimeter holding the sensor at a constant height above the water
- Software: mission planning for the flight lines, and hydrographic packages that turn soundings into models and capacity curves
Exact instrument selection is part of the pre-survey assessment: turbidity, depth and bed conditions at the chosen reservoirs decide which frequency and sounder type is appropriate.
How a survey runs
Pre-survey assessment
Historical data, satellite imagery, boundary identification and mission planning.
Drone-based survey
Bathymetric system deployment, RTK/PPK positioning and bed-data acquisition.
Validation
Conventional reference checks on selected areas.
Data processing
Bathymetric model, contours, depth and sedimentation maps, Elevation–Area–Capacity curves.
Final technical report
Reservoir-specific results, capacity and sedimentation assessment, and GIS outputs.
The proposed pilot
Two to three representative reservoirs, chosen jointly with the Department to vary in size, depth, siltation level and turbidity, surveyed over eight weeks:
- Weeks 1–2: pre-survey assessment and mission planning
- Weeks 3–5: drone-based field survey across the pilot reservoirs
- Week 6: validation against reference measurements
- Weeks 7–8: data processing and reservoir-specific final reports
No commercial commitment is sought at this stage. Cost and implementation model are matters for discussion only after the pilot has been evaluated.
What the Department receives, per reservoir
- Digital bathymetric survey dataset
- Digital elevation / bathymetric model
- Reservoir depth map and bed-contour map
- Present water-spread analysis
- Updated Elevation–Area–Capacity curves
- Present storage-capacity assessment
- Sedimentation and siltation assessment
- Comparison with historical capacity data
- GIS-compatible digital datasets and a technical survey report
Quality assurance
Establishing a QA methodology for Telangana’s reservoir conditions is the pilot’s real output, and every dataset ships with a stated confidence range.
RTK/PPK positioning
Survey-grade horizontal and vertical accuracy.
Instrument calibration
Checked before and during each deployment.
Reference surveys
Cross-checks against conventional measurements.
Uncertainty quantification
A stated confidence range with every dataset.
Beyond the pilot
Repeated across the state, the same method builds a Telangana reservoir capacity database: present-day capacity rather than historical assumptions, siltation quantified reservoir by reservoir, a data-driven case for desiltation where it is needed, and a repeatable standard for periodic resurvey.
Discuss the pilot
We are happy to present the programme in detail, or to walk through the methodology with your technical team.