Maurice, L., Taylor, R.G., Tindimugaya, C. et al. Characteristics of high-intensity groundwater abstractions from weathered crystalline bedrock aquifers in East Africa Hydrogeol J (2018). https://doi.org/10.1007/s10040-018-1836-9
From the GroFutures Consortium project and Groundwater Recharge Catalyst project
Crystalline Bedrock aquifers underlie about 40% of Sub-Saharan Africa and can generally sustain low-intensity abstraction. However, pumping rates and dependency is increasing in many areas, particularly for cities like Addis Ababa, Dakar, Nairobi and Dodoma. Projected growth in population and water demand for agriculture, plus the effects of climate change, mean that it is essential to develop a better understanding of the sustainable yields from these types of aquifers.
- The study focuses on five groundwater abstraction boreholes, 3 in Uganda, 2 in Tanzania.
- Long term groundwater records are only available for one of the boreholes and it shows that recharge happens more when the rainfall is more intense, which is often associated with periodic El Niño Southern Oscillation (ENSO) events.
- Chemical analysis of the water was used to determine the residence times of the groundwater (how long the water has been in the aquifer since it fell as rain). Overall, that most pumped water comes from modern recharge (within the last 10-60 years), so while abstractions are not mining pre-modern groundwater, there may be a component of older water that is coming out.
- Groundwater abstraction appears to be supported by recharge from across multiple years, rather than just the most recent wet season.
- The investigation of the five sites shows that long term, high intensity groundwater abstraction is possible from East African weathered crystalline basement aquifers, but the sustainability is constrained, in part, by the high inter-annual variability in recharge. Therefore operation of such pumping stations needs to include sustained monitoring of groundwater levels, pumping rates and rainfall as a minimum.
A research team, led by Prof. Alan MacDonald of BGS, has been awarded research funding by the UK Natural Environment Research Council (NERC) for a study entitled “Monitoring the impact of the 2015/16 El Nino on rural water insecurity in Ethiopia: learning lessons for climate resilience“
El Niño is a prolonged warming of sea surface temperatures in the central and east-central Pacific that occurs irregularly at 3-6 year intervals. El Niño weakens the trade winds and alters the monsoon pattern which affects global weather patterns and typically results in drought conditions in Southern Africa and Southeast Asia and enhanced rainfall in Eastern Africa and South America.
Continue reading New El Niño research grant awarded to UPGro investigators
re-posted from Grofutures.org
On April 4th and 5th 2016, members of the GroFutures Team visited the Makutapora Wellfield in central Tanzania to observe up close and with project partners, WamiRuvu Basin Water Office of the Ministry of Water, rare flood conditions that are associated with the 2015-16 El Niño Event and, it is expected, conditions favourable for episodic replenishment of the wellfield by recharge. In advance of the El Niño Event, the GroFutures Team established high-frequency sensors to monitor both surface water and groundwater levels resulting from what was expected to be anomalously heavy rainfall associated with the 2015-16 El Niño Event. The team was not disappointed by the rain but road conditions did present challenges to the downloading of data from installed sensors! After getting stuck twice in the very wet roads, the team will return again later in the year when conditions are drier. Nevertheless, a lot was learned from seeing the wellfield basin in flood.
Under the heading “Using groundwater to reduce poverty” the GroFutures Team in Tanzania led by Japhet Kashaigili, Andrew Tarimo and Devotha Mosha hosted the GroFutures Inception Workshop in Iringa on March 31st 2016. It was opened by the District Commissioner for Iringa, Hon. Richard Kasesela, and was attended by national, basin-level and local stakeholders (listed below) who discussed current groundwater use and management in the Great Ruaha Sub-Catchment of the Rufiji Basin and as well as both proposed and potential groundwater development pathways that might best reduce poverty. The event was featured on national television news in Tanzania (see clip here) and leading newspapers.
The GroFutures team is working with the Tanzanian Ministry of Water to establish automated, high-frequency monitoring to examine how heavy rains associated with the El Niño Southern Oscillation (ENSO) replenish vital groundwater resources.
The team from Sokoine University of Agriculture (Japhet Kashaigili, PhD student Richard Festo) and UCL (Richard Taylor, PhD Student David Seddon) are working with the WamiRuvu Basin Water Office in a small semi-arid basin (Makutapora) in central Tanzania which features a wellfield that supplies the capital city, Dodoma, with safe water. Groundwater withdrawals have risen sharply in recent years and there is considerable uncertainty regarding the sustainability of this supply. Previous research led by members of the GroFutures Team showed that replenishment occurs episodically, on average just 1 year in 5, and usually in association with El Niño events.
In anticipation of the “Godzilla” El Niño event this year, the team is setting up instruments to monitor hourly groundwater levels and river stage (level) to investigate how heavy rains replenish groundwater at the Makutapora Wellfield. These observations will inform not only sustainable management of wellfield itself but also strategies for amplifying replenishment here and in other similar tropical semi-arid locations.