Normalized Difference Vegetation Index (NDVI)

"The normalized difference vegetation index (NDVI) is a standardized index allowing you to generate an image displaying greenness, also known as relative biomass. This index takes advantage of the contrast of characteristics between two bands from a multispectral raster dataset—the chlorophyll pigment absorption in the red band and the high reflectivity of plant material in the near-infrared (NIR) band.

The documented and default NDVI equation is as follows:

NDVI = (NIR - Red) / (NIR + Red)

    NIR = pixel values from the near-infrared band
    Red = pixel values from the red band

This index outputs values between -1.0 and 1.0." (ESRI, 2018)

Sources

"Indices gallery". ArcGIS Pro, ESRI. 2018. 
http://pro.arcgis.com/en/pro-app/help/data/imagery/indices-gallery.htm.
Accessed February 1, 2019.

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Digital Earth Africa learning platform

This learning platform helps users understand the significance of Earth observations, explore Digital Earth Africa datasets through an interactive map, and get started on the basics of python coding for spatial analysis.

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Space-based Solution

Collaborating actors (stakeholders, professionals, young professionals or Indigenous voices)
Suggested solution

Background information on the geology of Kenya

The geology of Kenya shows Metamorphic rocks in the western part due to high metamorphic processes. The Great Rift Valley is a plate boundary.

Tertiary and Quaternary Volcanic Rocks: East African Rift System: volcanic activity during these periods

Geology map of Kenya
Fig.1: National Atlas of Kenya - Geological Map. (n.d.). European Commission, Joint Research Centre. ​

Resources used for addressing the challenge

Map of community locations

Map of important community locations
Figure 2: Map of locations of the community, from where water access would be needed in the vicinity.
Legend of the map of community locations

Software

  • QGIS: A Free and Open Source Geographic Information System. Version 3.32.3 / Version 3.28.11 LTR. 
  • ArcGIS Pro. Version ArcGIS Pro 3.

Data sources

Publications used for methodology and background research

see references indicated below.

Steps outlining the solution

  1. To find where water is situated, compare a topographic map with the Normalised Differentiated Vegetation Index (NDVI). Recharge occurs where water accumulates and hence vegetation is available/the healthiest at the driest times. This step could be implemented using Google Earth Engine.
     

    Topographic map of Samburu province in Kenya
    Figure 3: Topographic map of Samburu province in Kenya. Credit: Topographic Map (2023)

     

    Map showing the Samburu county Normalised difference vegetation index
    Figure 4: NDVI made with QGIS. Version 3.32.3 / Version 3.28.11 LTR.
  2. Develop a geology map and potentially a geophysical survey (mineral composition). Mineral data and geophysical characteristics are well mapped in Kenya. It is likely that the geology in Kenya requires a basement rock drilling using air hammers / air compressors and pneumatic hammering.
     
     Figure 3: Zoom into Samburu county from the National Atlas of Kenya - Geological Map. (n.d.). European Commission, Joint Research Centre.
    Figure 5: Zoom into Samburu county at the National Atlas of Kenya - Geological Map. (n.d.). European Commission, Joint Research Centre. Orange: Basement rock, Yellow Quarternary Sediments.

     

  3. The communities are located in the South-West of Samburu County. The geology in the area is mostly magmatic and metamorphic. This suggests that the ground has very low permeability. However, near the location of the communities there are two springs. These springs point to an aquifer in the area, where a well for the communities in the area could be developed. ---
    Map of water sources in Samburu county, Kenya.
    Figure 6: Water sources in the Samburu county. Map provided by Kenya Space Agency. Source: G. de Sourza, Dept. Geography, University of Nairobi, J. Keza, Ministry of Water Development.

     
  4. A desk study compares the geology with the topography
     
    Geology map of Samburu County Krhoda et al. (2015).
    Figure 7: Geology of Samburu County Krhoda et al. (2015).

     

Samburu county elevation map
Figure 8: Elevation Map made with QGIS. Version 3.32.3 / Version 3.28.11 LTR.

Location of water sources

The area of interest has two springs, which are natural groundwater outflow in the surface.

Map showing the Samburu county water points
Figure 9: Elevation Map made with QGIS. Version 3.32.3 / Version 3.28.11 LTR.

 

Groundwater resources

Aquifer in magmatic/metamorphic basement: moderate productivity

  • magmatic rocks have low permeability
  • Groundwater recharge is low

Ideal outcome: A possible groundwater source exists near the communities homes and borehole could be developed

Map showing possible groundwater resources in the Samburu County based on the geology
Figure 10. Possible groundwater resources in the Samburu County based on the geology.

 

Next steps to be taken with external actors

  1. Work with hydrogeologists to prepare a borehole siting report as well as an Environmental Impact Assessment. Groundwater relief has some trusted hydrogeologists in their network in Kenya who could implement that and submit the information to the Kenya Water Resources Agency.
     
  2. Kenya Water Resources Agency needs to grant permission for drilling.
     
  3. Drilling and pumping test: A contractor performs drilling and a pumping test. The latter is to identify the appropriate pump to be used.
  4. Groundwater level, type of aquifer, groundwater recharge, groundwater vulnerability.

 

Other solutions based on space technology and geophysics

List of commonly used geophysical methods in hydrology and geophysical properties they sense
Source: Binley et al., 2015.

 

Electromagnetic and seismic solutions

Electromagnetic and seismic solutions, image showing saprolite thickness in meters, the depth to bedrock in meters, and the water capacity of the aquifer in m.
Figure 11: Good results in hard rock terrains: metamorphic and magnetic rock areas. Source: Flinchum et al. (2018).

 

Relevant publications
Related space-based solutions
Sources

Barasa, M., Crane, E., Upton, K., Ó Dochartaigh, B.É. & Bellwood-Howard, I. (2018): Africa Groundwater Atlas: Hydrogeology of Kenya. British Geological Survey. Accessed [22.09.2023]. http://earthwise.bgs.ac.uk/index.php/Hydrogeology_of_Kenya

Kuria, Z. (2013): Groundwater Distribution and Aquifer Characteristics in Kenya. Developments in Earth Surface Processes, Elsevier. 16, 8, p. 83-107.

Krhoda, G., Nyandega, I. & Amimo, M. (2015): Geophysical investigations of Suyien Earthdam in Maralal, Samburu County, Kenya. International Journal of Physical Sciences. 2, p.33-49.

Makinouchi, T., Koyaguchi, T., Matsuda, T., Mitsushio, H. & Ishida, S. (1984): GEOLOGY OF  THE NACHOLA AREA AND THE SAMBURU HILLS, WEST OF BARAGOI, NORTHERN KENYA. African Study Monographs, Supplementary Issue 2, p. 15-44.

Touber, L. (1986): Landforms and solid of samburu District, Kenya. A site evaluation for rangeland use. The Winand Staring Centre for Integrated Land, Soil and Water Research. Report 6. 

Data sources (maps)

National Atlas of Kenya - Geological Map. (n.d.). European Commission, Joint Research Centre. https://esdac.jrc.ec.europa.eu/content/national-atlas-kenya-geological-map (visited: 19.10.2021). 

Samburu District - Type and Location of Water Sources, Key Landforms, and Soils (Symbols - See Map 11). (n.d.). European Commission, Joint Research Centre. https://esdac.jrc.ec.europa.eu/content/samburu-district-type-and-location-water-sources-key-landforms-and-soils-symbols-see-map-11 (visited: 19.10.2021)

Keywords (for the solution)
Climate Zone (addressed by the solution)
Dry
Habitat (addressed by the solution)
Region/Country (the solution was designed for, if any)
Relevant SDGs