Contribution to the assessment of European River Basin Management Plans

3.3 Oxygen-depleting substances (BOD) and suspended sediments

3.3.1 Methodology

The approach followed for nutrients and chemicals can be generalized to any constituent. In particular, the GREEN model will be generalized to BOD and TSS (hence GREEN+). BOD and TSS reflect similar conditions of uncertainty.

3.3.2 Spatial and temporal resolution

See § 3.1.2 and 3.2.2.

3.3.3 Input

Sources of sediments are assumed to follow the pattern of the JRC European soil erosion map¹⁰.

Emissions of BOD can be estimated from information on point and diffuse sources of pollution as for GREEN. Observed sediment concentration and BOD data are needed to calibrate the model. The data available in the EEA’s Waterbase¹¹ will be used as a starting point. More datasets, including data reported under the WFD by member states, will be tested insofar as available. For suspended sediments, data from the scientific literature collected by the JRC will be also used.

3.3.4 Preliminary assessment

None.

3.3.5 Previous applications

None.

3.3.6 Strengths

See § 3.1.6 and 3.2.6.

3.3.7 Weaknesses

See § 3.1.7 and 3.2.7.

3.3.8 State of play

Sediment and BOD model development will start in the month of May 2016 in the context of FP7 project Globaqua.

4. Flow regime

4.1 Methodology

The model used for all hydrological assessments is LISFLOOD. This is a full-blown spatially distributed hydrological model taking into account water abstractions in the water balance. With a hydrological model of this type, it is possible to compute several indicators of flow regime alteration, including water exploitation indexes and the number of days when flow is below a natural flow percentile, due to abstractions (see par. 4.4).

4.2 Spatial and temporal resolution

Model resolution is 5 km all over Europe, allowing in principle to describe every single water body with a catchment area of 25 km2 or more. The model works at daily time step.

4.3 Input

Along with the typical input of hydrological models (data on soils, land use, weather forcing, and water discharge data used for model calibration), the model relies on estimates of water abstractions. At present, these are derived from existing water demand datasets applied in the context of the impact assessment of the Blueprint to Safeguard Europe's Water resources (Communication from the Commission COM(2012)673)¹². These datasets include:

- livestock

- industrial and energy sector

- household

- irrigation.

Demand is typically estimated by spatial disaggregation of the latest Eurostat-reported data, when available. The irrigation demand is estimated as simulated precipitation deficit using a crop growth model.

4.4 Preliminary assessment

LISFLOOD has been used to produce indicators of flow regime alteration (number of days in the year when discharges fall below the natural 10%-ile or 25%-ile), as well as the Water Exploitation Index (WEI+) for consumption and for abstractions, i.e.the ratio of consumed water (or abstracted water) to renewable water availability. Figure shows examples of these indicators based on the model output version currently available¹³. The two indicators represent metrics of hydrological alteration, often used in the assessment of large regions when specific targets of environmental flow requirements are not defined.

Figure – above: flow regime alteration; below: WEI for consumption and abstractions, respectively.

4.5 Previous applications

LISFLOOD is extensively used for applications ranging from flood forecasting, to drought assessment, to climate change impact studies, to analysis of water resources. In particular, the model has been at the core of the impact assessment of the Blueprint to Safeguard Europe’swater resources.

In recent times, LISFLOOD output is being exploited for the European Water Accounts kept by the EEA.

4.6 Strengths

The model can be regarded as the most extensively calibrated operational pan-European flow discharge model, and has proved to perform satisfactorily across scales from the single catchment to continental or global level.

4.7 Weaknesses

The model allows a comprehensive representation of the terrestrial water cycle. However, particularly for the assessment of flow regime alterations due to abstractions, it depends directly on the representation of the latter. At present, water use and abstraction data in Europe are not commonly available, and if available are generally not distributed in space but aggregated by administrative units or basins. This limits the possibility of accurately describing the effects of these pressures.

4.8 State of play

A full recalibration of LISFLOOD has been completed in the first quarter of 2016.
5. Hydromorphological alteration

5.1 Methodology

We propose to characterize hydromoprhological alterations through two types of indicators addressing:

- the level of naturalness or alteration of floodplains

- the presence of dams and other stream barriers.

The former include the % of floodplains under natural, agricultural or artificial land use, and the density of infrastructure in the floodplains.

The latter include the % of drainage area of a stream that is intercepted by dams, and the % of the stream length that is free from dams (or other stream barriers).