Rainwater harvesting

"The collection of rainwater from a surface that allows for the rainwater to be stored and used at a later time. In a typical rainwater harvesting situation, rainwater is collected from an impervious surface such as the roof of a building and then stored inside of a tank or cistern. Rainwater can be collected from other surfaces as well. Other surfaces include parking lots, roadways, driveways, and even land surfaces (once surface runoff from the land surface begins). Rainwater can be harvested and stored for many uses including landscape irrigation, potable and nonpotable indoor use, and stormwater management. Harvested rainwater can be particularly useful when no other source of water supply is available, or if the available supply is inadequate or of poor quality." (Innovative Water Solutions, 2019) 

Sources

Innovative Water Solutions. 'What is Rainwater Harvesting?', by Chris Maxwell-Gaines. Accessed March 13, 2019. Available at: https://www.watercache.com/faqs/rainwater-harvesting-defined

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European Space Agency’s “Water Scarcity” Kick-Start

The challenge

Water is one of the most important substances on Earth and covers 70% of the planet. However, freshwater makes up a very small fraction with 97% being saline and ocean-based. While the amount of freshwater on the planet has remained fairly constant over time, the world’s population has exploded, meaning that freshwater is threatened by significant forces, like overdevelopment, polluted runoff, and global warming. 

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Describe your professional (and/or personal) experience relating to water (and space technologies). Please indicate whether an experience is related to water or to both, space and water).

I have always had an interest for science and the environment and before starting university I was introduced to hydrology which really caught my interest and led me to studying a BSc Degree in Hydrology and Geography.

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Stakeholder

Remote Sensing, GIS and Climatic Research Lab, University of the Punjab

The emerging demand of GIS and Space Applications for Climate Change studies for the socio-economic development of Pakistan along with Government of Pakistan Vision 2025, Space Vision 2047 of National Space Agency of Pakistan, and achievement of UN Sustainable Development Goals (SDGs) impelled the Higher Education Commission of Pakistan (HEC) to establish Remote Sensing, GIS and Climatic Research Lab (RSGCRL) at University of the Punjab, Lahore, Pakistan.

Person

Space-based Solution

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

Suggested solution   

Rainwater harvesting is a crucial solution for water scarcity in semi-arid countries like Kenya. Kenya’s arid and semi-arid lands (ASALs) cover 80% of its territory, making rainwater harvesting essential. There are various reasons why this approach can be beneficial in Samburu County.  

  • Water Scarcity Mitigation: Semi-arid regions face unpredictable rainfall and frequent droughts, exacerbated by climate change. Rainwater harvesting captures the little rainfall received, providing a reliable water source. 
  • Sustainable Water Supply: Rainwater harvesting techniques include small planting basins, trenches, stone bunds, and grass strips. These structures redirect runoff toward crops and pastures. By capturing rainwater, communities can sustain livestock, crop production, and domestic needs. 
  • Environmental Resilience: Droughts in Kenya are becoming more frequent due to environmental degradation and climate change. Rainwater harvesting helps mitigate
  • the impact of these droughts.  
  • Cost-Effective and Low-Tech: Rainwater harvesting doesn’t require complex infrastructure. It utilizes existing resources effectively. 

Outline of the solution

Steps to be taken: 

  1. Rainy season identification: the rainy season in the selected area needs to be identified. Further, the precipitation data from the past three to ten years needs to be studied.
  2. A geological study needs to be developed, this includes the study of the geology of the region, the development of geological maps, digital elevation model (DEM) maps, and normalized difference vegetation index (NDVI) map. 
  3. Precipitation maps of the location need to be developed. 
  4. Site Selection: Identify suitable locations for rainwater harvesting. Factors such as rainfall patterns, topography, and proximity to communities need to be considered. Choose areas with consistent rainfall during specific seasons. 
  5. Catchment area: Determine the catchment area where rainwater will be collected. Common catchment surfaces include rooftops, roads, or open fields. Ensure that the catchment area is clean and free from contaminants. 
  6. Conveyance system: Design an efficient system to channel rainwater from the catchment area to storage facilities. Components include gutters, downspouts, pipes, and first-flush diverters. Proper sizing and maintenance are crucial. 
  7. Storage tanks or reservoirs: Select appropriate storage options based on community needs. Common choices include: 
  8. Roof catchment tanks: Placed near buildings to store rainwater from rooftops. 
  9. Ground-level tanks: Buried or partially buried to store larger volumes. 
  10. Rock catchments: Natural depressions or excavated pits lined with impermeable materials. 
  11. Consider tank capacity, material durability, and accessibility for maintenance. 
  12. Water quality and treatment: Rainwater may contain impurities. Implement filtration systems to improve water quality. Use first-flush diverters to discard initial runoff (which may contain debris). 
  13. Climate resilience: Adapt the project to changing climate conditions. Monitor rainfall patterns and adjust storage capacity accordingly. 

Accomplished progress

Steps 1 - 3 have been successfully accomplished. Step 2 was developed in another space-based solution.

  • Rainy season identification 
    Decadal Precipitation in Kenya
    Figure 1: Decadal Precipitation in Kenya. Precipitation information during 21-31 December 2023. (Source: Dekadal Rainfall (meteo.go.ke))

     

    • Precipitation data from at least the last three years: CHRIPS  
    Decadal rainfall data
    Figure 2: Decadal rainfall in mm from July 2020 to July 2023. (Source: Dekadal Rainfall (meteo.go.ke))

     

    •  Digital elevation Model (DEM)
    Samburu DEM map
    Figure 3: Precipitation DEM map made with QGIS. Version 3.32.3 / Version 3.28.11 LTR. 

     

    • Precipitation maps 
    samburu precipitation map
    Figure 4: Precipitation map from 2023 made with QGIS. Version 3.32.3 / Version 3.28.11 LTR. The yellow areas indicate heavy rainfall, the green areas indicate moderate rainfall. 

     

    samburu precipitation map
    Figure 5: Precipitation map from 2024 made with QGIS. Version 3.32.3 / Version 3.28.11 LTR. The yellow areas indicate heavy rainfall, the green areas indicate moderate rainfall.  

     

    Development of precipitation maps 

    To create a precipitation map in QGIS, raster data representing precipitation values is needed. Therefore, the data is added to a raster layer in the QGIS project. 

    Steps to create a raster layer to map precipitation data: 

    1. Obtain precipitation data: First, obtain precipitation data from a reliable source in a compatible format. Common formats for precipitation data include GeoTIFF (.tif), NetCDF (.nc), or ASCII grid (.asc) files. 
    2. Open QGIS: Launch QGIS on your computer. QGIS is open for download: Download QGIS  
    3. Add Raster Layer:  
    • Go to the "Layer" menu and select "Add Layer"> "Add Raster Layer". 
    • Or click the "Add Raster Layer" button in the toolbar. 
    • Alternatively, use the shortcut Ctrl+Shift+R. 
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    1. Browse for Precipitation Data: In the "Data Source Manager" dialog that appears, navigate to the directory where your precipitation data is stored. 

    1. Select precipitation data file: Select the precipitation data file for the map. Make sure to choose the correct file format that matches the data (e.g., GeoTIFF, NetCDF, ASCII grid). 

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    6. Add Layer to the map: Once the precipitation data file is selected, click "Open" or "Add" to add the raster layer to your QGIS project. 

    7. Display the precipitation map: Now that you've added the precipitation data as a raster layer, you can visualize it on the map canvas in QGIS. Depending on the spatial resolution and coverage of your precipitation data, you may need to zoom or pan the map to view the data effectively. 

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    Once the precipitation data is added as a raster layer, the map layout can be customized to include legend, latitude and longitude factors, title, and other properties using the Print Layout functionality.  

    1. Open Print Layout: Go to the "Project" menu and select "New Print Layout" to create a new print layout. Give your layout a name and click "OK". 

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    2. Add Map to Layout: In the print layout view, click on the "Add Map" button in the toolbar, then click and drag to create a rectangle where the map is to appear on the layout. 

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     3. Add Legend: Click on the "Add Legend" button in the toolbar, then click and drag to create a rectangle where the legend is to appear on the layout. 

    4. Add Title: Go to the "Layout" menu and select "Add Item" > "Label". Click and drag to create a rectangle where the title is to appear on the layout. Double-click on the label element to edit the text and customize the font, size, and style. 

    5. Add Other Elements: You can add additional elements such as scale bars, north arrows, text boxes, images, and annotations using the "Add Item" menu in the toolbar.  

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     6. Add Latitude and Longitude Grid: Go to the "Layout" menu and select "Add Item" > "Map Grid". Click and drag to create a rectangle where the grid is to appear on the layout. ​ 

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    • Configure Grid Properties: Double-click on the grid element to open the "Item Properties" panel. Here, you can configure various properties of the grid, including: 
    • Grid Type: Choose between "Frame and Annotations", "Grid Lines", "Annotation Only", or "Frame Only" depending on the desired appearance. 10

       

    • Interval Units: Choose the units for the grid intervals (e.g., degrees for latitude and longitude). 
    • Interval X and Y: Set the interval for latitude and longitude gridlines. 
    • Annotation X and Y: Choose whether to annotate the gridlines with latitude and longitude values. 11

    • Customize Appearance (Optional): You can further customize the appearance of the gridlines, such as line style, color, and labeling options, using the options available in the "Item Properties" panel. 12

    Export and save: the layout can be exported to various formats such as PDF, image files, or print directly from QGIS. 

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    Future steps

    Steps 5-13 will be developed once step 3 (site selection) has been developed: 

    • Determine if enough water can be stored during the rainy season to last the dry season.
    • Determine seasonal river location and river width: determines the optical data that can be used (due to spatial resolution) 
    • Sediment load of the river 
    •  outcrops in bed and bank:  Ideally don’t want to have to excavate >5m deep    
    • Existing scoop holes on the river existing far into the dry season (indicates good water storage already) 
    • Vegetation on the banks (indicates localized water source) 
    • Slope of riverbanks (shouldn’t be too shallow) 
    • Slope of riverbed (ideally 1 - 5 %) 
    • Stream length 
    • Catchment area (from DEM) 
    • Location of faults and fractures  

    Finally, for the implementation of the rainwater harvesting plan, sediment samples from the selected seasonal river need to be studied. 

    Relevant publications
    Related space-based solutions

    Flood modeling for melting glacier - need for input

    Identify upstream potential pollution sources - in development

    Surface water extent river course - in development

    Construction of sand dams for Samburu County - in development

    Rainwater harvesting in Samburu County – in development

    Determining optimum sites for rainwater harvesting - in development

    Vegetation classification for land of Maori communtiy - in development

    Water suitability map (Samburu County, Kenya) - in development

    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