36 terms defined
A
- AEMET
- Spain's State Meteorological Agency (Agencia Estatal de Meteorología). The public agency responsible for weather forecasting and monitoring in Spain.
C
- Cold drop
- Popular term used to refer to a DANA. Although not technically identical, the two terms are often used as synonyms in everyday language.
- Concentration time
- Time it takes for water to travel from the most distant point of a basin to its outlet. It determines how quickly the basin responds to rainfall.
- Hydrographic Confederation
- River-basin authority under MITECO responsible for water management in each Spanish hydrographic district.
D
- DANA
- Isolated Depression at High Levels (Depresión Aislada en Niveles Altos). A mass of cold air detached from the general circulation that generates great atmospheric instability and torrential rainfall, especially in the Mediterranean.
- Dam
- Structure built to retain water, forming a reservoir. Spain has more than 1,200 large dams.
- Discharge release
- Controlled release of water from a reservoir through spillways or bottom outlets.
F
- Flood
- Temporary inundation of land that is not normally covered by water, caused by overflowing watercourses, accumulation of runoff, or rising water table.
- Flood event (avenida)
- Sudden rise in a river's flow rate, generally caused by heavy rainfall. Also called a "spate" or "flood wave".
- Flood routing
- Process of reducing the peak flow of a flood event by temporarily storing part of the volume in a reservoir or other regulating structure.
- Flow rate
- Volume of water passing through a section of a watercourse per unit of time. Measured in cubic meters per second (m³/s).
- Freeboard
- Free volume in a reservoir specifically reserved to absorb flood volume, reducing peak flow downstream.
G
- Gauging
- Measurement of a river's flow rate at a given point. Gauging stations continuously record water level and convert it to flow rate using rating curves.
- Gully (rambla)
- Normally dry watercourse typical of semi-arid Mediterranean areas that can carry large flows during storms. They are especially dangerous because of their innocuous appearance.
H
- Hietogram
- Graph showing the temporal distribution of precipitation (rainfall intensity over time).
- Hydrograph
- Graph showing the variation of a river's flow rate over time. The basic tool for analyzing and predicting floods.
- Hydrographic basin
- Territory whose surface waters drain to a common point (the outlet). Spain has 9 large inter-regional basins.
- Hydrology
- Science that studies the distribution, movement, and properties of water on Earth, including the hydrological cycle and runoff processes.
I
- Infiltration
- Process by which rainwater penetrates the soil through its surface. Infiltration capacity depends on soil type, antecedent moisture, and vegetation cover.
M
- Muskingum
- Hydraulic flood-routing method that simulates how a flood wave propagates and attenuates as it moves along a river reach.
P
- Precipitation
- Any form of water falling from the atmosphere to the Earth's surface: rain, snow, hail, or sleet.
- Rain gauge
- Instrument that measures the amount of rainfall accumulated over a period of time, expressed in liters per square meter (l/m²) or millimeters (mm).
- Rainfall station
- Sensor that measures the amount of precipitation fallen at a point. Automatic stations transmit real-time data to the SAIH.
- Return period
- Average interval (in years) between two hydrological events of equal or greater magnitude. For example, a flood with a 500-year return period has a 0.2% probability of occurring each year.
R
- Rating curve
- Mathematical relationship between water level and flow rate at a point in the river, calibrated with direct measurements.
- Reservoir
- Body of water retained by a dam. In addition to supply and irrigation, it serves a flood-routing function by holding back part of the flood volume.
- Runoff
- Rainwater that does not infiltrate into the ground and flows across the terrain surface toward watercourses.
S
- SAIH
- Automatic Hydrological Information System (Sistema Automático de Información Hidrológica). A network of telemetry sensors managed by the Hydrographic Confederations that transmits real-time precipitation, water level, and flow rate data.
- SCS-CN
- Soil Conservation Service method for estimating runoff generated by rainfall, based on a curve number that reflects soil characteristics and vegetation cover.
- Spillway
- Structure on a dam designed to evacuate water in a controlled manner when the reservoir reaches high levels. A key safety component.
- Stage gauge (limnimeter)
- Instrument that measures the water level in a watercourse. Continuous-recording stage gauges are called limnigraphs.
T
- Threshold
- Flow rate, water level, or rainfall value that, when exceeded, automatically triggers an alert level in the monitoring system.
U
- UME
- Military Emergency Unit (Unidad Militar de Emergencias). A unit of the Spanish Army specialized in responding to natural disasters, including floods.
W
- Warning level
- Threshold value of flow, water level, or rainfall above which a given degree of warning is activated (green, yellow, orange, red).
- Weather radar
- Remote-sensing instrument that detects precipitation by emitting microwave pulses and analyzing the reflected signal (reflectivity).