Climate and hydrology - Mediterranean Mountain Environments - page 92

et al., 2009) but limited to certain Mediterranean mountain zones. It is important
in future to improve the density and standards of snow-related measuring tech-
niques, including automatic meteorological stations, combined with high-resolution
remote sensing, altimetry satellite sensors and digital photogrammetry for monitor-
ing snowpack and estimating snowmelt in addition to 3D modelling techniques.

5.2.1 Rivers

Mediterranean rivers usually have extreme regimes, with very low summer dis-
charge and higher winter discharge reflecting the prolonged dry summers and wet
winters. The unit discharge of Mediterranean rivers varies considerably between 0.3
and 20 L/s/km 2 , according to the geographical and topographical location within
the Mediterranean Basin. Discharge can be very erratic, reflecting both floods and
droughts, whereby flood flows can be several hundred orders of magnitude higher
than normal flow (de Jong et al., 2008). Most river flow is highly regulated through
dams and reservoir storage. The existence of ephemeral or seasonal streams and
rivers is another special characteristic of Mediterranean hydrology that determines
the uniqueness of the relevant ecosystems. Irregular river flow poses particular water
resource challenges with respect to the application of the European Union Direc-
tives (Skoulikidis, 2009).

5.2.2 Snowmelt hydrology

This chapter will focus mainly on the more neglected snowmelt regimes of the
Mediterranean. The importance of snow and snowmelt in Mediterranean mountain
hydrology is often underestimated, although it is already the parameter most af-
fected by climate change. Snowmelt acts as an important trigger for floods and is an
major contributor to river discharge in the Mediterranean (Strasser and Etchevers,
2005). Many rivers that have their source at higher elevations, that is in mountainous
catchments, are dominated by snowmelt discharge. According to CIESM (2006),
the ratio of peak to annual discharge is often one order of magnitude greater com-
pared to rivers in non-Mediterranean areas. Snowmelt can delay maximum spring
discharge to April/May due to the strong groundwater component (e.g. the Drini
in Albania or Ceyhan river in Turkey). In the Seyhan river basın in Turkey, 62 %
of annual precipitation falls in the period between December and May (Gurer and
Turksoy, 1981). There is an accentuation of seasonal contrast towards the south and
east of the Mediterranean. However, there are exceptions in the west; for exam-
ple, the Mouloya in Morocco has one of the strongest seasonal contrasts in snow
discharge regime.
The snowmelt contribution to discharge (estimated at 25-30%) plays an impor-
tant role in many major Mediterranean rivers yet precise quantification of snow
and glacier-melt contribution to discharge is still relatively poor (see Table 5.2).
This preliminary table (Table 5.2) was compiled by the authors and it shows that