Overview

Project Highlights:

 

  • Student has opportunity to undertake multidisciplinary field data collection in a remote rural area and hence gain a wide range of transferrable skills.
  • Project has high impact potential due to engagement of partner NGOs, working in areas where there is an acute need for improved water sources.
  • Potential for high impact journal papers in the water resources field.

Overview:

Semi-arid lands are home to 14% of the world’s population (UN Decade 2018), with this figure set to rise under a changing climate.   In these areas, rain falls in one or two intense periods in the year, so harvesting rainwater and storing it for the dry season is an essential water management strategy.   Water can be stored in tanks or used to artificially recharge the groundwater.   Sand dams are an example of a managed aquifer recharge structure, similar to check dams except that they trap both water and sediment (“sand”) behind them. Previous studies have focussed on the sand dam as an isolated water storage structure and recent studies by Cranfield University (Quinn et al 2018a) have only just revealed the extent to which water typically flows between the trapped sand and the surrounding aquifer.   This study will evaluate the impact that the sand dam has on the surrounding area and in doing so address important questions about the wider impacts of managed aquifer recharge structures which could be applied in any semi-arid region where shallow groundwater is being augmented   The focus will be in Makueni County in Kenya as this has one of the highest concentrations of sand dams globally.   The impacts to be evaluated will include:

  • Water levels – wells are often dug into the area adjacent to a sand dam.
  • Water salinity – the area is underlain by Mozambique Gneiss which is locally highly variable in petrology and weathering.   This gives a complex local pattern of groundwater salinity (Quinn et al 2018b).   Water collected from the trapped sand is typically less saline than water in the surrounding aquifer, although the water infiltrating from the trapped sand may have a dilution effect, which will be a focus of this study.
  • Vegetation - as the shallow groundwater is recharged, vegetation will increase, soil erosion will decrease and biodiversity will increase.
  • Local microclimate – the increase in vegetation may also change the local microclimate and mitigate natural climatic fluctuations.

Sand dams are part of a broader socio-environmental system with local communities using water for their domestic, agricultural and livelihood needs. This research will also seek to understand how their practices interact with broader hydrological process and try to systematically bring these factors together. As climate change will increase temperatures in this region of Kenya, sand dams also have the potential to help communities adapt, by increasing water availability into the dry season.

 

Methodology

The study will involve both fieldwork and remote sensing components.  

The fieldwork will involve monitoring existing sand dams, as well as studying sand dams that are being constructed.   Monitoring will include measuring water levels in wells and installed piezometers, as well as taking samples for water quality measurement. Surveys will be conducted with local communities to understand the impacts of the sand dams on the amount of water they collect and the time spent collecting it and assess how their behaviours may shape or interact with the hydrological system.

Remote sensing will include Landsat data which will be used to understand changes in vegetation since the sand dam was constructed.   A network of Waterpoint Data Transmitters (Thomson et al 2019) are currently being installed on handpumps near to sand dams which will provide real time data on water collection.   This data will need to be ground-truthed and compared to the field monitoring in order to fully understand the impacts of sand dams.

Training and Skills

Depending on their background, the student will be encouraged to attend modules from the Water and Sanitation for Development and Geographical Information Management MSc courses, including Surface and Groundwater Hydrology, Water Source Engineering, Communities and Development and Physical Processes of Remote Sensing.   Training in field data collection will be provided by supervisors Dr Alison Parker (water levels and quality) and community surveys (Dr Paul Hutchings). Visiting Prof Ken Rushton will also provide mentoring.   Training in Waterpoint Data Transmitters will be provided by the University of Oxford as part of their DFID/NERC UpGro grant.

Timeline

Year 1: Student training, initial analysis of Waterpoint Data Transmitter data (collected since February 2019), visits to pre-construction sites, detailed monitoring and community survey planning.   First field campaign (after rainy season) May-July 2020.

Year 2: Ongoing analysis of Waterpoint Data Transmitter data.   Analysis of monitoring data and water balance construction.   Analysis of Landsat data.  Second field campaign May-July 2021.Year 3: Final impact monitoring at selected fieldsites, final analysis, thesis writing.

 

Partners and collaboration (including CASE)

The main partners will be the UK-based NGO Excellent Development and their local partner, Africa Sand Dam Foundation.   Excellent Development have built over 1000 sand dams to date and plan to influence the implementation of 10,000 dams for 5 million people by 2025 (Excellent Development 2017). They have been partners of Cranfield since 2015.  

Further Details

Alison Parker a.parker@cranfield.ac.uk

https://www.cranfield.ac.uk/research-projects/sand-dams

The student will be based at the Cranfield campus at Cranfield in Bedfordshire - https://www.cranfield.ac.uk/About/How-to-find-Cranfield