In Mediterranean climates, mild year-round temperatures support comfortable human settlement with rich agricultural regions. The climate’s long summer drought, seasonal river flow, high inter-annual variability in precipitation and episodic floods threaten these settlements, leading to highly manipulated hydrologic systems. The degree of hydrological alteration and consequent ecological change is typically much greater in Mediterranean climate rivers than humid-climate systems¹. Dams, diversions, irrigation channels, storage and distribution facilities simultaneously restrict flow regimes, support economic development and destroy the native biological communities in the Mediterranean.

Overcoming the complex relationships among climate, economy and our entangled legal and political institutions challenge the restoration potential of Mediterranean climate river systems worldwide.

CALIFORNIA AND PORTUGAL
In California, the endangered steelhead and smelt fish populations continue to decline in highly-altered river systems that strain to supply water to a growing human population. Of the 1,853 water bodies in mainland Portugal, 40% are classified as “at risk,” including surface waters of the Rio Real basin, while another 20% of water bodies have insufficient data. The extent of ecological deterioration remains elusive as scientists and policy-makers struggle to develop methods and plans without understanding of pressures and impacts, baselines, and relationships between land use and water quality.

Water quality goals are often framed as the critical chemical issue to be resolved with wastewater treatment plants and reduction in non-point source pollution. The wider scope of ecological impacts caused by hydro-morphological alterations, however, rise to the forefront as major obstacles for Mediterranean climate river restoration efforts due to the important economic services provided by water infrastructure. Typically, high-maintenance levees for flood
protection, dams for water storage and hydropower, and diversions for agriculture irrigation are managed by multiple overlapping agencies with conflicting mandates. Portugal has the largest area of irrigated agriculture in the EU. Agricultural interests cover only 25% of irrigation costs.

While the European Water Framework Directive (WFD) promises a streamlined institutional structure with the scope and authority to develop and regulate basinscale management plans, the long-standing local needs for flood defense, water treatment and water supply infrastructure will be implemented by municipalities, land owners and farmers on the ground. Collaboration with researchers in other Mediterranean climate regions holds promise for defining solutions.

¹ Batalla et al 2004; Kondolf and Batalla 2006 drainage basins.

J. Natali, G.M. Kondolf, C. Landeiro, J. Christian-Smith, S. Scheuer, and T. Grantham
January 2009 |  47 Pages

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