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Episode recorded August 29, 2022
Episode released on April 6, 2023
Alan MacDonald is the Head of Groundwater at the British Geological Survey and is stationed in Edinburgh. His focus mostly is on groundwater development and management in developing countries for poverty reduction, and water security.
Highlights | Transcript
- Recent study tilted “A Century of Groundwater Accumulation in Pakistan and Northwest India” (Nature Geoscience) documents groundwater storage increase of at least 420 km3 over the 20th century. Groundwater level monitoring data show increases in storage from 1900 – 1970, followed by a stable period, with declines from 2000 – 2010 of 70 km3 related to intense groundwater fed irrigation. The increase in groundwater storage since 1900 is 4 – 5 times greater than the decrease in 2000 – 2010. This was like the largest unmanaged aquifer recharge project globally.
- This study provides much longer-term context to the recent declines in storage recorded by GRACE satellites over the past two decades.
- The cause of groundwater level increases was attributed to water leakage from huge irrigation canals with construction expanding substantially from the 1850s to 2000. This emphasizes the importance of surface water – groundwater interactions.
- Human intervention rather than climate change was the cause of the groundwater storage changes. Increases in the early 1900s occurred despite decadal droughts in that time.
- Drilling boreholes and accessing groundwater provides much more control to the farmer with up to 10 million boreholes in the IndoGangetic Aquifer, increasing crop yields with up to 3 crops in a year.
- Boreholes initially were shallow (20 – 30 m) but are getting deeper (50 – 100 m) but this alluvial aquifer is much thicker (up to 1 km thick).
- Ganges Water Machine: deliberately lowering groundwater levels near the Ganges to increase storage space to capture flood flows during the wet season, idea from 1970s, currently being considered by World Bank.
- Water quality issues include increasing salinity with shallow groundwater linked to flooding and locally arsenic, fluoride and uranium issues.
- Deep groundwater pumping might cause transport of contaminants from the shallow system, such as nitrates, pesticides, and organics because the shallow and deep systems are connected, unlike in Bangladesh where they are separated by thick clay layers.
- British Geological Survey working directly with National Institute of Hydrology and Central Groundwater Board to translate science to policy.
- Paper on “Quantitative maps of groundwater resources in Africa“ published in Env. Research Letters in 2012; first study to provide estimates of groundwater availability, 100 times greater than annual renewable surface water.
- Results picked up by media globally, helped African partners communicate importance of groundwater to government ministers and others. BBC Huge Water Resource Exists under Africa.
- Huge thick aquifers in North Africa, e.g., Nubian Aquifer etc but interested in thin localized aquifers where people live, crystalline basement aquifers covering 40% of the continent, weather up to 50 m deep, provide water to community water systems and limited irrigation.
- Also need to consider groundwater recharge: low recharge in North Africa where aquifers are thick and storage high but higher recharge in basement aquifers replenishes groundwater fairly regularly.
- Drilling successful boreholes in basement aquifers is tricky, geophysics and experienced hydrogeologists are extremely valuable.
- Work on hand pumps: about half of them not functioning, variety of causes: not constructed properly, too shallow, too deep, cannot get replacement parts, community management not working, need expertise and capital for operations.
- Groundwater underdeveloped in Africa, unlike India and some other regions.
- Outcome of 2012 mapping: 7 yr research program UPGRO (Unlocking the Potential of Groundwater in Africa) capacity development in Africa, 150 scientists in 5 large projects. Hand pump project, Hidden Crisis. Use of groundwater to improve agriculture GroFutures.
- Groundwater excellent resource to develop resilient water resources, especially in areas where surface water is limited.
