Preserving Tank Cascade Systems to build Agroecological Landscape Resilience in the Dry Zone of Sri Lanka (Special article on
International Mother Earth Day)
Sri
Lanka’s tank cascade systems promote an important traditional water management
strategy that has been used for centuries to build agricultural resilience in
the dry zone. These are a series of small reservoirs or tanks that are
interconnected through canals, designed to capture and store rainwater during
the wet season and provide irrigation water during the dry season and a part of
Sri Lanka’s hydraulic civilization. These systems interconnect small human-made
reservoirs which capture seasonal rainwater for agriculture, household, and
environmental purposes and are considered the lifeblood of communities in the
Dry Zone of Sri Lanka. Tank cascade systems have helped to address drought and
flood mitigation historically. They help to build agricultural resilience in
the dry zone, those are:
Sustainable
water supply:
tank cascade systems provide a sustainable water supply for irrigation,
particularly during the dry season when rainfall is limited. This can help to
reduce crop losses due to water stress and increase agricultural productivity.
Drought
mitigation:
tank cascade systems can also help to mitigate the impact of droughts by
storing water during the wet season and releasing it during the dry season.
This can help to ensure that crops have access to water during periods of
prolonged drought.
Increased
crop diversity:
tank cascade systems can support increased crop diversity by providing water
for a range of crops, including paddy, vegetables, fruits, and spices. This can
help to reduce the risk of crop failure due to pests or diseases and provide a
more varied and nutritious diet for local communities.
Improved
soil fertility:
tank cascade systems can also improve soil fertility through the deposition of
sediment and nutrients in the tanks and canals. The use of organic fertilizers
and other CSA practices can further enhance soil fertility, leading to
increased crop yields.
Cultural
heritage preservation: tank cascade systems are an important part of Sri Lanka’s
cultural heritage and have been maintained and improved over centuries by local
communities. The preservation and promotion of these systems can help to
maintain cultural traditions and support sustainable livelihoods for rural
communities.
Tank
cascade systems are remarkable and one of the most efficient water management
systems in the world. In ancient times, these systems functioned sustainably,
in harmony with the environment, and were maintained by the communities that benefitted
from them.
The CSIAP
initially planned to develop 122 cascades in 11 districts in Sri Lanka. For
that, the CSIAP has already completed the Participatory Rural Appraisal (PRA) at
the tank level, hydrological assessments including the water balance study,
engineering survey, and prepared Hotspot Area Agriculture Development Plans
(HSAADPs) based on the 47 agrarian service centre divisions covering 256 GN
divisions in 11 districts and 06 provinces. With the reduction of project funds
during the country’s economic crisis, CSIAP is able to develop nearly 60
cascades only with available funds. The following table explains the ongoing
tank rehabilitation and cascade development in climatically vulnerable hotspot
areas in Sri Lanka.
The Cascade
development is not a simple intervention. As I already mentioned, the intervention
is interrelated with multiple sectors, multi-disciplinary subjects, and multi-stakeholders.
Therefore, CSIAP is be careful when taking the steps to develop the cascades in
climatically vulnerable hotspot areas. According to the community’s point of
view, the rehabilitation of tanks and the cascade developments are related to
the livelihood of the people, the balance of ecosystems including biodiversity,
and the prevention of disasters etc. People from the community say that “when
you touch the tank or cascade for the rehabilitation intervention, you must
think that you are touching the heart of the community in the village. Tanks
and cascade are not a physical infrastructure, those are feeling of the
community”.
As
I already mentioned, CSIAP started the tank rehabilitation and the cascade
development interventions by doing multiple studies, surveys, and screening to
ensure that no harm to the ecosystem and the community in the climatically
vulnerable hotspot area. To avoid and prevent the impacts and the risks, CSIAP
conducted the PRA, hydrological assessments, engineering survey, HSAADP, PIR,
and environmental and social screening for the cascades and the tanks in the
climatically vulnerable hotspot areas. The cascade development is an integrated
intervention. Therefore, CSIAP ensured that tank rehabilitation and cascade
development works are done without harm to the ecosystem and the community.
CSIAP
is rehabilitating and developing the different types of tanks in a cascade with
different functions (forest tanks, tanks for water purification/ silt trapping,
tanks for seasonal cultivation with no permanent settlements, and village tanks).
A village tank consists of many components, each serving a specific purpose to
maintain the integrity and hydrological connectivity of the system. With the absence
of this integrity, the small tank cascade systems fail to deliver the ecosystem
services and socio-cultural benefits such as the provision of water for
irrigation and other domestic uses, water purification, groundwater recharge,
flood management, erosion control, provision of food, medicines, raw materials,
recreational benefits, cultural and spiritual bonding, habitats for wildlife,
and carbon sequestration.
The components of a village tank are a stream (seasonal stream), a filter (a strip of grass and
reeds on the periphery of the water body that acts as a filter to trap silt), a
water hole (an upstream sediment trap), a windbreak of trees (an area planted
with large trees that act as a windbreak to minimize evaporation from the
surface of the tank), soil ridge (an upstream bund to manage soil erosion and
sedimentation), and interceptor (the stretch between the tank bund and paddy
fields). This acts as a downstream wind barrier, reduces tank seepage, and prevents
sodium, magnesium, and iron from entering the paddy land, paddy field, and drainage.
We
can say that pocket of biodiversity can be identified in the tank cascade
system. Or we can say that tank cascade systems are rich in biodiversity. Tank
ecosystems create a mild microclimate that supports a variety of flora and
fauna that otherwise would not have inhabited the climatically vulnerable
hotspot areas. The long-term sustainability of tank cascades depends on the
holistic understanding of socio-ecological aspects and requires a
multidisciplinary and multi-stakeholder approach. In this way, CSIAP is
establishing the Cascade Management Committees (CMCs) with the relevant
stakeholders in climatically vulnerable hotspot areas in Sri Lanka.
It
is most important to point out that, the CSIAP always ensures the long-term
knowledge management and transparency of investments in tank management to ensure
community ownership. Also, the project is promoting community-centred tank
rehabilitation. We identified that more cost-effective compared to third-party
contracting.
The CSIAP
has conducted sufficient cascade-wise technical studies required before rehabilitation
work. Cascades-based approaches are helping sustainable agroecological
landscapes, cascade-based climate adaptation, and cascade-based disaster risk reduction.
In this project, we implemented a cascade-based approach for tank rehabilitation
and cascade development, while blending the scientific results with traditional
indigenous knowledge and practices. We successfully brought back the community
lead maintenance and management of tanks, without losing the vital contribution
made by the stakeholder agencies. The achievements of the project will be highly
significant. Key lessons learned from the CSIAP can be used about cascades in climatically
vulnerable hotspot areas on how to empower communities with the means and
knowledge to embrace their heritage and environment and become self-sufficient.
Article
Written By Sharmila Thirhiharan, Gender Development Officer,
Project
Management Unit, Climate Smart Irrigated Agriculture Project
Photographs by Deputy Project Director's Office (Southern)
