Millions of people in towns and cities across Sub-Saharan Africa depend on groundwater day-to-day – but is it safe to drink? How can we measure the safety quickly, cheaply and accurately? In this RWSN-UPGro webinar, Dr Jenny Grönwall (SIWI/T-GroUP) and Dr Dan Lapworth (BGS) present the latest updates on their research into urban groundwater monitoring and use, and how it can be improved.
The GroFutures Team, working with the Tanzanian Ministry of Water and Irrigation, expanded monitoring infrastructure in the Upper Great Ruaha Observatory (UGRO) to include interactions between groundwater and surface water.
An outstanding question regarding the sustainability of groundwater withdrawals for irrigation and drinking-water supplies is whether groundwater in the agriculturally intensive lowlands is replenished by river flow, sustains river flow, or both depending upon the season.
Re-posted from GroFutures.org
The GroFutures team at Sokoine University of Agriculture (SUA, Tanzania), led by Japhet Kashaigili (SUA) with support from PhD students, Hezron Philipo (SUA) and David Seddon (UCL), established in July (2017) a groundwater-level monitoring network in the Upper Great Ruaha Basin Observatory in southern highlands of Tanzania. This area is part of the Southern Agricultural Growth Corridor of Tanzania (SAGCOT) where increased use of groundwater and surface water is anticipated to support agricultural production. Constructed monitoring wells at depths ranging from 18 to 32 m below ground were drilled using a PAT-DRILL 421 rig. The team also instrumented monitoring wells recently constructed by project partners at the Rufiji Basin Water Board (RBWB) in the Tanzanian Ministry of Water and Irrigation.
The new monitoring network comprises an upstream location at Chimala at the base of an escarpment and a downstream location at Mbarali within the alluvial plain. A monitoring well at Chimala Secondary School was installed into coarse unconsolidated sands and gravels to a depth of 26 m. This monitoring well is linked to both an additional monitoring well at Usangu Secondary School and a river gauge. Both monitoring wells are equipped with automated dataloggers providing hourly groundwater-level measurements. A third borehole was constructed at Chimala Primary School though no groundwater was encountered up to a depth of 30 m. At Mbarali, two monitoring wells were constructed on the St. Ann’s Secondary School and now form a transect of 4 monitoring wells as the team also instrumented two monitoring wells recently constructed by the RBWB at Rujewa at Mbarali Secondary School and Jangurutu Primary School.
The new infrastructure is expected to reveal for the first time the dynamics between groundwater and surface water in the Upper Great Ruaha sub-catchment of the Rufiji Basin and answer key questions around the nature of groundwater recharge and whether seasonal river flow recharges groundwater or groundwater sustains river flow. Further work will also seek to ensure that this observatory is equipped with both tipping-bucket rain gauges to record sub-daily (hourly) rainfall intensities and soil-moisture probe arrays to better understand how intense rainfalls are transmitted through alluvial soils.
Shallow groundwater wells, are the main source of drinking water in many rural and peri-urban communities.
The quantity and variety of shallow wells located in such communities make them more readily accessible than private or government operated deep boreholes, but shallow wells are more susceptible to faecal contamination, which is often due to leaching pit latrines.
For this reason, online monitoring of water quality in shallow wells, in terms of faecal pollution, could dramatically improve understanding of acute health risks in unplanned peri-urban settlements.
More broadly, inexpensive online faecal pollution risk monitoring is also highly relevant in the context of managed aquifer recharge via the infiltration of either stormwater or treated wastewater into the subsurface for aquifer storage and recovery.
To tackle this challenge, IN-GROUND – an UPGro Catalyst Project – trialled four different types of Microbial Fuel Cell (MFC) water quality biosensor in the lab (Newcastle University, UK) and in the field (Dar Es Salaam, Tanzania).
While further work is needed, the results provided proof-of-concept that these biosensors can provide continuous groundwater quality monitoring at low cost and without need for additional chemicals or external power input.
Full details of the work can be founded in this open access paper: Velasquez-Orta SB, Werner D, Varia J, Mgana S. Microbial fuel cells for inexpensive continuous in-situ monitoring of groundwater quality. Water Research 2017, 117, 9-17.
For more details contact Dr Sharon Velasquez-Orta
The UPGro programme, supported by AfriWatSan & ESPRC, conducted a pan-African capacity-strengthening and knowledge co-production workshop at Sokoine University of Agriculture in Morogoro, Tanzania from the 10th to 12th of February, 2017.
40 participants from 12 countries in Africa took part and analysed multi-decadal, groundwater-level data (“chronicles”) from 9 countries including Benin, Burkina Faso, Ghana, Niger, Sénégal, South Africa, Tanzania, Uganda and Zimbabwe.
The simple up-and-down motion of hand pumps could help scientists secure a key water source for 200 million people in Africa.
Growing demand for groundwater is putting pressure on the resource while researchers struggle to accurately estimate the future supply.
But a team from Oxford University says that low-cost mobile sensors attached to pumps could solve the problem.
Their study shows that pump vibrations record the true depth of well water.