Wetlands & Biodiversity

The environmental sector is an important water user; and one that often finds itself at the bottom of the list of priorities when supplies become scarce. One component of IWMI's Water, Health and Environment research looks at how the needs of wetlands and other ecosystems can coexist with parallel human and irrigation demands.

Water maintains natural ecosystems, which sustain biodiversity, help to regulate the hydrological cycle and bring value to people in the form of goods and service derived from activities in these ecosystems.

It is increasingly being recognized that one of the costs of large-scale irrigation is the draining of wetlands or reduced river flows that starve wetlands of their water. In other cases the inflow of irrigation drainage into wetlands changes water quality and water levels—negatively impacting plant and animal life.

IWMI research in this area is working to scientifically document the relationship between irrigation water management and the environment (especially wetlands) in an integrated manner, focusing on practical solutions to quantify and manage irrigation water flows that can sustain ecosystems while obtaining optimum agricultural production.

IWMI works with both irrigation and nature conservation groups; the aim is to bridge the gap between these two sectors, which often are in conflict.

Smakhtin, V.U.; Piyankarage, S.C.; Stanzel, P; Boelee, E. 2004. Simulating the hydrology of small coastal ecosystems in conditions of limited data. Research Report 77, Colombo, Sri Lanka

Piyankarage S C, Mallawatantri, A P, Matsuno Y and Pathiratne K A S. 2002.
Estimation of nitrogen and phosphorus fluxes to Embilikala and Malala lagoons in southern Sri Lanka. pp. 9-20. In Janaka Ratnasiri (ed.). Assessment of Material Fluxes to the Coastal Zone in South Asia and their Impacts. Proceedings of the APN/START/LOICZ South Asia Regional Workshop, Negombo, Sri Lanka. 08-11 December 2002. The Sri Lanka National Committee of IGBP, Colombo, Sri Lanka. 2003.

Kite, G., P. Droogers, H. Murray-Rust, and K. De Voogt. 2001. Modeling scenarios for water allocation in the Gediz Basin, Turkey. Colombo, Sri Lanka: IWMI. v, 29p. (IWMI research report 50)
Available on-line in HTML and PDF formats.
To order the print version: send your request and postal address to iwmi.publications@cgiar.org

DE Voogt, K., G. Kite, P. Droogers, and H. Murray-Rust. 2000. Modeling water allocation between wetlands and irrigated agriculture: Case study of the Gediz Basin, Turkey. Colombo, Sri Lanka: IWMI. xi, 51p. (IWMI working paper 1)
Available on-line in PDF format, 8,991KB; requires Adobe Acrobat Reader™.
To order the print version: send your request and postal address to iwmi.publications@cgiar.org.

Kite, G. 2000. Developing a hydrological model for the Mekong Basin: Impacts of basin development on fisheries productivity. Colombo, Sri Lanka: IWMI. v, 141p. (IWMI working paper 2)
Available on-line in PDF format, 10,925KB - requires Adobe Acrobat Reader™.
To order the print version: send your request and postal address to iwmi.publications@cgiar.org

  • Expansion without extinction: how can biodiversity be preserved in irrigation systems?
    Understanding the impact of irrigation development on biodiversity and identifying potential strategies for conservation. more information>>

  • Sustainable management of wetlands in southern Africa for poverty alleviation
    Examining the long-term sustainability and productivity of low-lying shallow groundwater aquifers in Zimbabwe, Malawi and other Southern African countries. more information>>

  • Modeling water allocation between wetlands and irrigated agriculture: a case study from the Gediz Basin, Turkey
    Identifying water allocation regimes that balance the needs of wetlands and irrigated agriculture.
    more information>>

  • Hydrologic modeling of the Mekong River Basin for environmental impact studies
    Developing a hydrologic modeling tool that can be used to explore the impacts of water management decisions on water levels and the consequent impacts on fish life and other aquatic species. more information>>
  • Impacts of irrigation water on coastal wetlands: a case study from Sri Lanka
    Determining how changes in water quality due to irrigation drainage flows impact the presence of birds and other species in downstream lagoons. more information>>

What are the impacts of upstream irrigation on coastal wetlands? How can these impacts be minimized?

Bundala National Park, a Ramsar Convention wetland in Southern Sri Lanka, hosts a vast population of wildlife, migratory birds, and aquatic life. IWMI recently studied the interactions between the wetland and the upstream irrigation project.

The research showed that:

  • Pesticides and fertilizers used by farmers in the irrigation scheme flow into the lagoons along with irrigation drainage water. Because of the elevated nitrogen and phosphate levels, eutrophication is an emerging problem in the lagoons.

  • The changing water levels affect birds and other wildlife. And the inflow of drainage water has disturbed salinity balances, resulting in fewer shrimp maturing in the lagoons. Shrimpers periodically cut the sandbanks separating the lagoons from the sea to achieve a direct increase in salinity.

Based on these findings, the Irrigation Department of Sri Lanka has introduced a rotational water supply. This minimizes water losses to the sea and diminishes the impact of irrigation drainage on coastal lagoons. Other options include: reducing drainage flows by more closely matching the amount of irrigation water supplied to crops' actual needs. Preliminary modeling studies suggest that fertilizer applications could also be reduced without affecting crop yields.

The World Resources Institute's Earth Trends provides access to extensive databases, maps, country profiles and feature articles on a number of topics linked to wetlands and biodiversity.

Click here for more on-line resources

last updated: 19 September 2003

Findings and recommendations
Links to on-line resources

How can we determine the amount of water natural ecosystems need?

What are possible strategies for ensuring wetlands receive the water they need, without decreasing the yields from irrigated agriculture and poor farmer's incomes?

How can developing countries meet the need for expanding agricultural areas without sacrificing biodiversity?

How can the damage to wetlands caused by flows from irrigated areas be reduced?

How do we value ecological goods and services?

In the eutrophication process water becomes enriched in dissolved nutrients, such as nitrates and phosphates, that stimulate the growth of aquatic plants. This usually results in the depletion of dissolved oxygen needed by fish and other organisms. Eutrophication is an emerging problem in many lagoons and lakes due to the inflow of nutrients from water draining from agricultural areas or industrial or municipal wastewater.
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