Rapid Assessment of Zanzibar Groundwater Resources

Sub-Saharan Africa urged to explore potential of Groundwater

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The Quest for Sustainable Freshwater Resources in Zanzibar

Sub-Saharan Africa is believed to host large groundwater reserves that remain unutilized. The SADC Groundwater Management Institute estimates that the 16 member states of the Southern Africa Development Community have groundwater reserves amounting to at least 2.5 million litres per year (at least 2491m3 / capital / year), which exceeds that of Europe and Asia. Despite this, the institute noted that the region utilizes only 1.5% of its potential groundwater reservoir. The SADC Water Division on the other hand reports that, only 61 per cent of the region’s population has access to clean water, mainly due to poor infrastructure. This implies that the other 40 percent is exposed to unclean and unsafe water sources.

The Tanzanian autonomous archipelago region of Zanzibar is grappled with this challenge. In order to have a better insight of the challenge, the Ministry of Water, Energy and Minerals of Zanzibar launched a study to undertake a rapid assessment of the groundwater potential in Zanzibar (Pemba and Unguja). The study was supported by SADC Ground Water Management Institute (GMI), Zanzibar Water Authority and Global Water Partnership under the technical guidance of Dr. Subira Munishi of University of Dar es Salaam.

The study highlighted that groundwater remains the major source of water in Zanzibar. This is because there are very few rivers that flow throughout the year while most of them have a short travel time after which they quickly infiltrate and disappear into the underground zone. The rapid assessment study also highlighted the continued deterioration of groundwater quality, mainly due to the nature of aquifers in the archipelago. The unconfined nature of the aquifers makes them to be highly prone to diffuse pollution from diverse anthropogenic activities. Dr. Subira showed through an elaborate mapping exercise that, settlement and urban dwellings are strategically located where the major aquifers and springs are; with the settlements being attracted by water availability but consequently threatening the sustainability of this vital resource.

The rapid assessment study revealed that most wells in Unguja, the largest island of the Zanzibar archipelago with a population of close to 900,000 people, have higher salinity values (amount of dissolved salts in water) that are two or four times above the permissible limits. In the southern part of Unguja, with the largest ground water reserves, water wells have salinity values as high as seven times above the recommended limits. The study also shows that springs and shallow wells in the Islands of Unguja and Pemba have very high levels of bacteriological pollutants mainly due to anthropogenic activities.

A sequential component of the rapid study, led by Ruden Water, focused on potential of off-shore submarine aquifers in meeting the water demands for Zanzibar. The initial modelling study indicated a potential of existence of under the sea aquifers that could be exploited. A detailed feasibility study is yet to be conducted to ascertain the cost-benefit analysis of exploiting the sub-marine aquifers to supply water in Zanzibar.

During the High-Level Water Investment Conference in Zanzibar which took place on 11th March, H.E. Jakaya Kikwete, Chair of the Global Water Partnership Southern Africa and Africa Coordination Unit (GWPSA-Africa) and former President of the United Republic of Tanzania emphasized on the need to explore groundwater resources as a solution to prevailing water insecurity challenges in the region. Notably, groundwater remains a cheaper option to water supply both for domestic and industrial use, unlike desalinated sea waters. Our experts just need to ensure groundwater is being tapped from sources that would last for years,” he said.

During the conference, Zanzibar President H.E. Dr. Hussein Mwinyi launched the Island’s $665 million Zanzibar Water Investment Programme (ZanWIP) of which was developed under a collaborative effort of different partners under the African Water Investment Programme (AIP). ZanWIP is the first water programme designed under the banner of the Continental AIP which is part of Programme for Infrastructure Development in Africa Priority Action Plan 2 (PIDA PAP2) led by AUDA-NEPAD in Africa.

Launching the Investment Programme, H. E Dr. Mwinyi said; “there was urgent need to mobilise US$ 665 million to finance and implement measures to narrow Zanzibar water investment gap to achieve the Vision 2050, in collaboration with local, regional, and global partners to respond to the increasing water demand as the economy grows and address pressures exacerbated by climate change impacts.”

During the same conference, Mr. James Sauramba, Director for SADC GMI said that seawater and groundwater are the major sources for water within the region but expressed concern over weak policies at national and transboundary levels to promote the use of surface and groundwater sources. “The surface water sources are dwindling, and groundwater seems to be resilient,” he said.

He said SADC GMI would support studies to understand how much the region can rely on groundwater, saying there was need to understand the recharge points which would inform sustainability and protect the sources from pollution since when groundwater is polluted, it’s difficult to save it. African countries need concrete solutions for investment opportunities to tackle specific challenges faced by Zanzibar, as well as those brought on by harsh weather patterns and poor water infrastructure.

Technical & Editorial Team

Dr. Subira Eva Munishi
University of Dar Es Salaam, Tanzania
Dr. Victor Kongo
Global Water Partnership Tanzania (GWP-TZ), Tanzania

Data Acquisition and Processing Team

Chrisogonous Kibugu
Research Assistant
Global Water Partnership Tanzania (GWP-TZ), Tanzania
Andrew Kimati
Earth Observation data scientist
Global Water Partnership Tanzania (GWP-TZ), Tanzania
Frankie Anderson
Environmental & GIS Technical Personnel
Global Water Partnership Tanzania (GWP-TZ), Tanzania

With generous support from

Global Water Leadership Programme