Spain’s Water Resources: Rivers, Regimes, and Management
Water Diversity and Resources in Spain
Water is an essential element for all natural ecosystems and supports a large number of human activities. Its presence and characteristics are influenced by various conditions: climate, relief and topography, lithology, vegetation, and human activity.
Hydrographic Regimes of Spanish Rivers
Several factors influence the characteristics of Spanish rivers:
- Climate: Climate, especially precipitation, determines the absolute volume and flow rate of rivers.
- Regime Types: Rivers can have snowy (nival), rainy (pluvial), or mixed (nivo-pluvial or pluvio-nival) regimes, depending on the dominant water source.
- Relief and Topography: Relief and topography determine the watershed, drainage basins, slope, erosion potential, and the feasibility of hydraulic works.
Hydrographic Slopes
- Cantabrian Slope: Rivers are short as they rise in mountains near the coast. They are generally abundant and fairly regular in flow. Dams (pantanos) are often built for hydroelectric power generation due to the climate and terrain.
- Atlantic Slope: Rivers are long, flowing through plains. They have an irregular regime with summer droughts and floods during autumn and spring rains.
- Mediterranean Slope: Rivers are generally short (except the Ebro), often forming gullies (ramblas). They have a very irregular regime with dry summers and catastrophic floods caused by torrential autumn rains. Intermittent watercourses (those that only carry water when it rains) are common.
- Balearic and Canary Islands: These archipelagos feature streams (arroyos) or torrents with low flow, often fed by springs. In the Canary Islands, exploitation of aquifers has reduced the number of surface streams. Torrents are frequent in both archipelagos.
Lakes
Lakes are bodies of fresh or saltwater accumulated in depressed areas, reaching a certain depth. We distinguish between:
- Endogenous Lakes: Formed by forces originating from inside the Earth (tectonic or volcanic).
- Exogenous Lakes: Formed by external processes (glacial, karstic, arheic, eolian, or coastal).
Wetlands
Wetlands are extensions of land covered by shallow water. They include ponds, marshes, deltas, estuaries, and peat bogs (turberas). They are of great biological interest as they host many animal and plant species adapted to live in a transitional environment between water and land.
Aquifers
Aquifers are pockets of underground water formed when infiltrating precipitation encounters an impermeable layer and accumulates. This often occurs in geological depressions, such as those from the Tertiary period. This groundwater is typically free from harmful organisms found in surface waters.
Water Use and Management in Spain
Water Balance and Challenges
Water is an essential resource used in numerous human activities. The water balance relates available water resources to consumption. In Spain, the overall balance is positive, although several problems exist:
- Uneven water availability across regions.
- Demand concentrated in developed areas.
- An inadequate network of dams for regulation.
- Significant annual water losses.
Water Policy and Planning
Water policy regulates water resources according to the Water Law, which governs all surface waters and the channels through which they flow within the national territory. Water resource management is carried out through water planning:
- River Basin Management Plans: Identify the needs and required works for each basin.
- National Hydrological Plan: Coordinates basin plans and designs the general water program.
- Hydraulic Works: Infrastructure created to regulate water resources and improve water quality. Examples include:
- Using Pyrenean lakes for hydroelectric energy production.
- Desalination plants (salt water treatment).
- Wastewater treatment plants.