Walia Special Edition on the Bale Mountains (2011) - Zoologische ...

Preliminary Results
All the lakes and ponds are situated well above the timber line, which is marked by Hagenia-
Hypercicum (2800 – 3200 m in the southwest, and 3300 – 3500 m in the northeast exposition).
On mountains north of the Bale range, such as Mt. Bada (4139 m), Mt. Abuye Meda (4305 m),
Mt. Choke (4070 m), Mt. Guna (4231 m), Abuna Josef (4190 m) and the Semien range (4548
m), lakes are either absent (Semien) or do not occur at altitudes above the timberline. Although
Garba Guracha, which is located in a side valley of the Togona River, is the only typical morainic
lake under investigation, there is no doubt that almost all of the lake and pond basins have been
influenced, if not formed, by glacial activity. Many basins have been completely filled up or filled to
such a degree that only very shallow and temporal water bodies remain.
A summary of selected physical and chemical data on the study sites is presented in Table
1. In brief, our Bale Mts study sites are located between 3917 and 4141 m elevation. They are all
permanent (i.e. they also hold water during the dry season), and fairly shallow (average water depth
of 29,1 cm during the dry season and 51,4 cm during the wet season ), except for Garba Guracha
which is distinctly deeper (5,2 m during the dry season, and 6,0 m during the wet season). High
water marks along the shoreline and GPS mapping of wet and dry season shorelines indicate that
water level can vary considerably between seasons (up to 1m), especially in the larger lakes like
Garba Guracha and Hara Laki (called Hora Orgona by Löffler 1978). Water bodies look visibly very
different during wet and dry season. More specifically, macrophytes are far less common and water
transparency is considerably lower during the dry season (often with large amounts of suspended
sediments). This is presumably due to the combination of wind-driven sediment disturbance during
the dry season, and the higher number of waterfowl during that time increasing nutrient content and
algal productivity. Several chemical parameters (such as total phosphorus,
<strong>Walia</strong>-<strong>Special</strong> <strong>Edition</strong> on the Bale Mountains 174