Nairobi
is experiencing a water crisis of the kind that lures environmentalists into
fits of gloomy Malthusian prognostications on demand and supply. For
Nairobians, running taps and showers are almost luxuries of a past they remember
with nostalgia.
The
water situation in Nairobi is scourge on our national pride. It undermines the
livability and attractiveness of the city. The nickname “The Green City in the Sun” now invites sniggers.
Less
than 50% of Nairobi’s residents have direct access to piped water and only 40%
have daily access to water. Only 22% of residents of the informal settlement,
home to 60% of Nairobi’s residents, have access to piped water. Furthermore, Nairobi
is insanitary; only 40% of Nairobi residents with access to the city’s water
and sewerage network water-borne sewage.
The
bulk of water supply for Nairobi comes via an old pipeline network from Ndakaini
in Thika, Sasumua in the upper ridges of the Aberdares, Kikuyu springs and
Ruiru in Kiambu. These sources are insufficient. The current demand for water
exceeds supply by about 377,000 cubic meters per day. The supply deficit is
exacerbated because 40-60% of the water destined for Nairobi is unaccounted
for, lost.
The
government, with funding from the French Development Agency and the World Bank undertook
a study to identify new water resources within a radius of 70km of the Nairobi.
The report, “Feasibility Study and Master
Plan for Developing New Water Sources for Nairobi and Satellite Towns”, recommends
groundwater development, abstraction and diversion of three rivers to supply additional
water to the Thika reservoir by 2017.
Sadly,
these new water resources will add a paltry 203,040 cubic meters per day, raising
the supply to 685,980
cubic meters per day in 2017, against a projected daily demand of 1 million cubic meters. Moreover, additional diversions,
abstractions and inter-basin transfers proposed between 2018 and 2030, but are
unlikely to meet the projected conservative demand of 2.5 million cubic meters
per day by 2030.
The
solutions proposed in the feasibility study and master plan – increasing supply
bulk volumes of portable water from outlying rural districts – were first
developed and applied in Europe in the 19th century. Cutting and
pasting solutions for Europe and North America from two centuries ago will not
solve the problems of a dynamic Kenyan city.
Meeting urban water needs in the 21st century will require a paradigm shift. 19th century
supply side solutions alone will not balance the ever-growing demand for water driven
by rapid urbanization, shortage of surface and ground water due to climate
change and competition from agriculture. Conventional
approaches to urban water needs are unlikely to support sustainable communities
and sustainable urban growth. The development of sustainable technologies and
demand management measures are urgently needed.
Cities are hotspots of water
consumption. But cities also have a huge potential to reduce their water
footprint. Simple, low cost distributed innovations can deliver phenomenal
reductions on urban water demand while creating new jobs in green plumbing and
ecological engineering, improving environmental quality and creating exquisite
habitat for urban flora and fauna.
I propose an approach that would reduce demand for centralized
portable water through water use efficiency, reuse, recycling and purification
of domestic wastewater, roof catchment and the abundant urban storm runoff.
Use of flush toilets (at 10-13 liters per flush) consumes nearly 40% of domestic
water. Mandating the installation and use of low flush toilet would reduce
water use per flush by 50%. Vacuum toilets use 0.5 liters of water per flush to
transport the same volumes of human waste. Besides delivering outstanding water
use efficiency, a dedicated vacuum sewer network connecting hundreds of
households of can generate biogas as produce fertilizer for agricultural use. Furthermore,
ecological sanitation approaches, which promote dry sanitation by separating
solid and liquid human waste, offer low cost, low-tech non-polluting effective
sanitation solutions for low-income urban households.
Greywater – wastewater generated from showers, baths, hand basins,
laundries and kitchens – is relatively easy to reuse. With minimal treatment,
in the form of physical filtering and settling, greywater can be reused for
toilet flushing and gardening. An ecological engineering approach through the
application of constructed wetlands and wastewater aquaculture can be used
effectively to for the treatment and purifying of wastewater and contaminated
roof and urban storm runoff.
Water quality cascading, an approach that aims to match water
quality to water use, is an important demand managing measure. Diversion of
grey water from hand washbasin, washing machine and showering to toilet
flushing is an example of water quality cascading.
Overall, national policy and institutional resources must focus on
providing a framework for an integrated understanding of the multiple
approaches to sustainable urban water and promote distributed, rather than centralized
than water and sanitation strategies. Such decentralized infrastructure will
play a vital role in water supply and demand while enhancing service quality
and accountability.
Hi Alex! Well said indeed! However we forget to think of the watershed and how water cascades and transitions from here to the end user. With this in mind, I want to advocate that in order for the city and its environs to have a sustainable supply, yes we will require innovative approaches in regards to greywater management, low flow toilets e.t.c. However the ultimate success lies in conserving the source of this water; the watersheds.
ReplyDeleteOnly then will we realize complete sustainability.Our organization is in the process of creating a model known as water funds in the Upper Tana watershed. You could think of it as a sort of trust fund where utility companies and large water users put funds into a kitty which are then re-directed to the watershed to facilitate conservation and incentivize the community to adopt better land management practices and alternative sources of income whose end goals are to preserve and conserve the green infrastructure in these watersheds.