Application of indicators of hydrologic alterations in the designation of heavily modified water bodies in Spain

In Europe, the Water Framework Directive (2000/60/EC) demands the achievement of a good ecological status for water bodies by 2015. However, it also defines exceptions to these objectives, such as a good ecological potential instead of a good ecological status or a more distant temporal horizon than 2015. Those exceptions may only be applied to heavily modified water bodies (HMWBs). This paper presents a method, P-IAHRIS, incorporated into the free software IAHRIS v2.2, that offers objective criteria for the preliminary designation of HMWBs downstream from irrigation dams, flood protection dams or drinking water supply dams. The procedure incorporates two indicators: (i) the P10%–90% indicator, which analyses the alterations in the flow regime associated with the range of natural variability defined by the 10th and 90th percentiles of the annual and monthly discharges; and (ii) the IHA-HMWB indicator, which assesses the changes in the magnitude, seasonality, variability and duration of natural flows. P-IAHRIS was applied to 103 water bodies in Spain. The functionality and versatility of the method have been proven and allow the fast and objective preliminary designation of HMWBs, both in the Mediterranean and Atlantic environments.

► New method for preliminary designation of heavily modified water bodies.
► Designation is based on the assessment of the hydrologic alterations of flow regime.
► The methodolgy is incorporated into the free software IAHRIS v2.2.
► Has allowed objective preliminary designation of 103 Spanish water bodies.