Bathymetric and Sedimentation Survey Project

Sedimentation survey

The need for sedimentation assessment.

Effective management of reservoir continuously require data on their current volume.  Volume loss occurs due to sedimentation.  In Kenya, sedimentation is a recurrent problem caused by anthropogenic accelerated soil erosion.  Post-impoundment sedimentation can be determined using multi-Frequency Acoustic Profiling System couple with vibro-coring technology.  This state of the art technology is now available in JKUAT through a collaborative initiative.

This collaborative initiative was set-off by joint effort of JKUAT, USDA-ARS and Baylor University in Waco TX.  Staff from these three institution wrote a proposal, which provided the seed money from USAID, to purchase part of the bathymetric and sedimentation equipment.  The Principal Investigator from JKUAT is Dr. Joseph Sang.  After the initial proposal other organizations have also partnered with implementation of the Project.  These organizations include the Nairobi City Water and Sewerage Company (NCWSC), World Agroforestry Centre (ICRAF) and Dresden University of Technology (TU Dresden).

Because of the collective effort of these organizations the bathymetric and sedimentation project was officially launched on 13th July 2015.  The project launching ceremony was officiated by JKUAT’s DVC-RPE, Prof. Esther Kahangi, NCWSC Managing Director Engineer Philip Gichuki and the Director WARREC Prof. Bancy Mati.

Bathymetric and Sedimentation assessment technique.

Sedimentation Assessment

Reservoir sedimentation assessment using Acoustic Profiling Technique and vibrocoring

The sedimentation status of Ruiru dam, Thika Dam and Lake Naivasha was established using Bathymetric Survey System (BSS). The BSS has a navigation system and multi-frequency acoustic system. The frequencies include 200 kHz, 50 kHz and 12 kHz. High frequency enables determination of surface of the sediment and low frequency penetrates through the deposited sediment layer to pre impoundment levels of the reservoir.  During the survey, the boat is driven in predetermined transects. The sounder which is mounted on a motor driven Dual-Jon-boats aids in establishing the water depths and the depth of recently deposited sediments.

The depth of recently deposited sediments is further confirmed by core samples collected at selected locations

Typical core samples from reservoir sedimentation

Typical core samples from reservoir sedimentation

using a vibro-coring device. The collected depth data are further processed to generate the water and sediment volume.

Core samples are then analyzed in laboratory which will aid in dating of the cores and establishing sources of the sediments within the watershed. Proper conservation practices within the watershed are modelled and identified then recommended to watershed managers in view of reducing the current sedimentation rate in reservoirs. Hydrological models, such as SWAT, are used to simulate the sedimentation and erosion/deposition hotspots.

Some of the current findings have found that Ruiru reservoir has lost about 12% of its storage capacity and preliminary results show that the quality of water is also being affected by sedimentation.

Summary of the current Bathymetric and Sedimentation project partners.

The project is being implemented in collaboration with

·         Soil Water and Environmental Engineering Department (SWEED)
·         Water Research and Resource Centre (WARREC)
·         United State Department of Agriculture- Agricultural Research Services (USDA-ARS) – Up to mid-2014
·         Dresden University of Technology (TU Dresden)
·         World Agroforestry Centre (ICRAF)

Bathymetric and Sedimentation assessment project activities.

April 2017 to May 2017:

Sedimentation conference

Summary of Presentations can be found here 

April 2017 to May 2017:

Laboratory analysis of sediment samples for physico-chemical parameters and dating.

March 2017:
Develop and Submit proposal for surveying Sasumua Reservoir for funding consideration.

December 2016 to January 2017:
Preparation of core samples for Laboratory analysis.

October 2016 to date:
post processing of bathymetry data.

August to October, 2016:
Bathymetry survey and sediment coring of Lake Naivasha, Oloiden and Crater lake.

JKUAT Investigators

Principal Investigator (PI)

Dr. Joseph Sang

Co-Principal Investigators

  • Dr. (Eng). James Messo
  • Prof. Urbanus Mutwiwa

Project Publications

  1. Maina, C. W., Sang, J. K., Mutua, B. M., & Raude, J. M. (2018). Bathymetry survey of Lake Naivasha and the satellite Lake Oloiden, using Acoustic Profiling System. Lakes and Reservoirs: Science, Policy and Management for Sustainable Use.
  2. Maina, C. W., Sang, J. K., Mutua, B. M., & Raude, J. M. (2018). A review of radiometric analysis on soil erosion and deposition studies in Africa. Geochronometria, 45(1), 10-19. doi:10.1515/geochr-2015-0085.
  3.  Maina, C. W., Sang, J. K., Mutua, B. M., & Raude, J. M. (2019). Geochronological and Spatial Distribution of Heavy Metal Contamination in Sediment from Lake Naivasha, Kenya. Journal of Radiation Research and Applied Sciences.
  4. Maloi, S. K., Sang, J. K., Raude, J. M., Mutwiwa, U. N., Mati, B. M., & Maina, C. W. (2016). Assessment of Sedimentation Status of Ruiru Reservoir, Central Kenya. American Journal of Water Resources, 4(4), 77-82.
  5. Ouedraogo, I., Sang, J. K., & Home, P. G. (2017). HEC-HMS Model for Runoff Simulation in Ruiru Reservoir Watershed. American Journal of Engineering Research, 6(4), 7.
  6. Sang, J. K., Raude, J. M., Mati, B. M., Mutwiwa, U. N., & Ochieng, F. (2017). Dual Echo Sounder Bathymetric Survey for Enhanced Management of Ruiru Reservoir, Kenya. Journal of Sustainable Research In Engineering, 3(4), 6.

Students participating in the Bathymetric and sedimentation assessment project

    1. Ms. Caroline W. Maina
    2. Mr. Stanley Maloi (Completed)
    3. Mr. Ismael OUEDRAOGO (Graduated)

 

Summary of past and current funding sources

Source Amount (KSh) Purpose
USDA-ARS 2,400,000* Purchase of custom made Dual Jon Survey boat.
JKUAT – RPE 4,497,048 Bathymetric and Sedimentation survey in Thika Reservoir and Lake Naivasha Survey
NCWSC 3,938,750 Bathymetric and Sedimentation Ruiru Reservoir
TUD 1,111,000** Sample analysis and travel to and from Germany

* Dollar equivalent
**Euro equivalent

updated November 2018