| Lake Eğirdir | |
| Pushpin Map: | Turkey |
| Coords: | 38.0567°N 30.8661°W |
| Basin Countries: | Turkey |
| Area: | 482km2 |
| Elevation: | 917m (3,009feet) |
Eğirdir (Turkish: Eğirdir Gölü, formerly Eğridir) is a lake in the Lakes Region of Turkey. The town of Eğirdir lies near its southern end, 107abbr=offNaNabbr=off north of Antalya. With an area of 482km2 it is the fourth largest lake in Turkey, and the second largest freshwater lake.
The town and the lake were formerly called Eğridir, a Turkish pronunciation of the town's old Greek name Akrotiri. Eğridir means "it is crooked" in Turkish, so to remove the negative connotations, in the mid-1980s the "i" and the "r" were transposed in a new official name, thus creating Eğirdir, a name that evokes spinning and flowers,[1] although many people in Turkey still call both the town and the lake by its former name.
Lake Eğirdir must have existed in ancient times, since coins from the nearby city of Parlaos have been found with ships on them, but no clear references to the lake have been found in ancient texts, and its ancient name is unknown. A number of ancient settlements have been located around the lake: places whose names are known were Eğirdir itself (historically known as Akroterion), Parlaos, Malos, and Prostanna; and places whose ancient names are not known were at the ruin sites of Bedre, Ghaziri, and Ertokuş Han, as well as on Yeşil Ada. (Based on its modern name, Bedre – now known as Gökçe – may have been called "Petra" in ancient times.) In the 14th century, Ibn Batutta mentioned merchant shipping on the lake at Eğirdir (or Akrīdūr, as he called the city in Arabic).[2]
Lake Eğirdir is fed by about 40 different springs, some of which are intermittent, and also by rainfall within its 3,309-km2 drainage basin. The main streams which feed Lake Eğirdir are the Pupa, the Hoyran, the Yalvaç, and the Çay.[3] Besides evaporation, water exits Lake Eğirdir either by flowing out through the Kovada Canal into Lake Kovada, by draining out into one of the about 20 natural ponors that exist at the bottom of the lake, or by being pumped out through one of the 11 irrigation pumps built around the lake. The average retention time for water in the lake is 2.5 to 3 years.[4]
The lake has an average depth of 7 m and a maximum depth of 13 m.[4] Significant fluctuations in Lake Eğirdir's water level are not uncommon.[2] It has a total volume of 4000abbr=offNaNabbr=off, of which 1000hm3 is drawn off for irrigation, drinking water, or other human uses.[4] Approximately 45,000 hectares are irrigated by waters drawn from the lake.[4] There is no thermal stratification in the lake.[4]
A strait called the Hoyran Boğazı divides Lake Eğirdir into two parts: the larger Eğirdir Gölü proper and the smaller Hoyran Gölü.[2]
Lake Eğirdir has two islands, connected to the mainland by a long causeway into the town of Eğirdir:
Beginning with Karekin Deveciyan's Türkiye'de Balık ve Balıkçılık in 1915, a total of 15 different fish species have been recorded in Lake Eğirdir.[5] Of these, 7 are endemic species that still inhabit the lake, 2 are endemic species that are now locally extinct, 4 are introduced species, 1 is of uncertain origin but is native to the area, and 1 is of unknown status but likely an exotic species.[5] Introduction of invasive species since the 1950s, along with overfishing, has caused significant disruption in the local ecosystem.[5] The first major change came in 1955, when the non-native pike perch, which preys on other fish, was intentionally introduced to the lake.[5] The reason was that the lake's native fish were not very economically valuable for commercial fishing.[4] The population dynamics of the lake's ecosystem "rapidly collapsed", and two endemic species became locally extinct.[5] Since then, other exotic species have been introduced to the lake, such as the omnivorous Prussian carp by 1996 and the plankton- and fish-eating big-scale sand smelt by 2003.[5]
Endemic species:
originally identified by Kosswig and Geldiay (1952) and Küçük (1998) as Nemacheilus angorae, Küçük et al. more recently said it should be classified as B. mediterraneus instead.[5]
Introduced species:
Uncertain origin, possibly or likely exotic:
not recorded in studies between 1933 and 1997; its first recording was by Küçük in 1998 in the Çayköy Canal.[5] Its origins are unknown, but Van Neer (1999) theorized that it may have accidentally been introduced when the lake was being stocked with other fish species.[5]
The narrow-clawed crayfish (Astacus leptodactylus) inhabits Lake Eğirdir and is commercially harvested.[6] It is not native to the lake, but when exactly it was introduced is unknown.[4] From 1970 to 1985, Lake Eğirdir accounted for 75% of Turkey's annual crayfish catch.[4] In 1986, however, the lake's crayfish population "collapsed" due to crayfish plague and crayfish harvesting stopped.[6] Its population later recovered somewhat and commercial harvesting was resumed in 1999; however, catch numbers have never recovered to pre-plague levels (harvests are "1 to 2 orders of magnitude lower than those in the early 1980s".[6] Another outbreak of crayfish plague in the lake in 2004 killed off much of the local population, and commercial harvesting of crayfish in Lake Eğirdir was banned in 2009.[6] The pathogen causing crayfish plague, Aphanomyces astaci, has remained present in the lake, which may have prevented the local crayfish population from fully recovering to previous levels.[6]
The total economic value of commercial fishing on Lake Eğirdir has ranged between a low of US$50,526 in 2008 and a high of US$3,001,920 in 1977.[4] The most profitable period was the decade from 1975 to 1985, when the annual yield ranged from $2–3 million USD.[4] The most important fish species have historically been the Eurasian carp and the pike perch, while crayfish were the most important species overall between 1975 and 1985.[4] Several native fish species such as V. vimba, C. pestai, and P. handlirschi were never economically significant.[4] Predation and overfishing have threatened the lake's Eurasian carp population, especially since the 2000s, and its annual catch has fallen by 90% from what it was in the 1950s.[4] From 2008 to 2012, commercial fishing of Eurasian carp was banned.[4] Pike perch fishery has also decreased in importance in recent decades as that fish's population has contracted.[4] The crayfish catch also plummeted in the 1980s due to the crayfish plague, and its harvesting was banned from 1986 to 1999 and again from 2008 to 2010.[4] In the 2000s, the introduced Prussian carp became a very successful source of commercial fishing.[4] However, the overall annual yield for the lake's fisheries have continued to decline.[4]
In terms of employment, the number of workers in the lake's fishing industry has increased continuously since 1991, and especially since 2001.[4] The number of households employed in fishing increased from 287 in 1991 to 1,164 in 2009.[4] The amount of fishing boats on the lake was 1,623 in 1984, 115 in 1999, 425 in 2001, and 510 in 2002.[4]
About 45,000 hectares of farmland are irrigated using waters from Lake Eğirdir.[4] Water is also extracted for drinking water and electricity generation, although in the 2000s this has decreased relative to the increasing agricultural demand.[4] The lake provides drinking water to the city of Isparta.[7]
Lake Eğirdir forms part of the Eğirdir-Kovada graben, a north–south depression that also includes Lake Kovada.[8] Two distinct stages of geological deposits are visible on dry land.[8] Deposits from the first stage are exposed above ground in the Yeşilköy area; this is called the Yeşilköy Formation.[8] This may have been deposited by the prehistoric Gölcük Volcano, 50 km to the southwest near the city of Isparta.[8] The second phase is recent alluvial sedimentary deposits from Quaternary times, especially visible in areas around Eğirdir and Barla as well as around Lake Kovada.[8]
This region is very seismically active; for example, in March 2007, a magnitude 5.1 earthquake happened on the lake's eastern shore, along the Esinyurt Fault; it was followed by 93 smaller aftershocks over a period of 4 days.[8]