Reservoirs Contributions

For each reservoir the minimum contribution received from the hydrologic year beginning is calculated weekly (the 1^st of October in hydrology is called “Julian day 1”) and they compare it with the average contribution received in the last 30 years at the same date (expected contribution).

This task allows us to know the type of hydrologic year every reservoir has had: very dry, dry, normal, wet and very wet.

For example, as the following diagram shows, the Guadalmena reservoir -located in Jaén province which basin goes along Albacete province- had collected 145,96 hm³ from the 1^st of October 2008 (Julian day 1) until the 1^st of August 2009 (Julian day 304). The average for the last 30 years in that date was 87,7 hm³Therefore the contribution received by the 1^st of August exceeds the expected contribution by 66%. It means a wet year for the contributing basin to such reservoir.

Somehow the Pintado reservoir located between Sevilla and Badajoz provinces by the 1^st of August had got a total water contribution of 39,4 hm³ whereas the average for such date in the last 30 years was 115,8 hm³ whereas the average for such date in the last 30 years was 115,8 hm³. That reservoir only got 34% of the expected contribution so we can deduce that the year has been a dry one for that section of the basin. We can see it graphically in the following diagram.

To evaluate the status of the basin as a whole we will repeat the same operation with the 37 main head reservoirs including the reservoirs from Iznájar, Negratín and Jándula because of their dimensions. The average historic contributions of these reservoirs have been recalculated to deduct the effect of the reservoirs located upstream. These dams collect rainwater from 23.546 km², 41% of the total territory thus its hydrology is representative of the whole Guadalquivir Basin.

In this case, if we take as reference the same date than in the above examples, the reservoirs that drained away such surface had collected a total of 2.296 hm³, in front of an average of 2.279 in the 1979-2008 period. This represents an increase of 3%. Therefore it has been a normal year for the whole basin although it is not a homogenous situation.

Para calcular el carácter del año hidrológico en curso respecto a la media, se aplica la siguiente expresión:

Where,
EH_{día n} is the indicator of the hydrologic status for day n of the ongoing hydrologic year,
A_{día n} is the contribution accumulated in day n of the ongoing hydrologic year, and
AH_{día n} is the average contribution accumulated in day n for the last 30 years period.

The following thresholds have been used for the years’ classification:

The following diagram shows the hydrologic status for the 10^th of April 2012 in relation with the historic average in the 1979-2008 period.

The hydrologic status map will be periodically updated in this space.