Barro Colorado Island (BCI)

BCI (9°10'N, 79°51'W) is an island which was isolated from the surrounding mainland in 1914 following the damming of the Chagres river and the formation of Gatun Lake. The island, rising 137m above Lake Gatun, has an area of 1500 ha which are covered by forest which has remained relatively undisturbed for at least 100 years. BCI forms part of the Barro Colorado Nature Monument (BCNM). For more information about STRI facilities on BCI and the BCNM click here.

Click here for a detailed geological description of BCI.
The island receives an average of 2623 mm of rain per year. Day-time temperatures reach an average of 32°C, with night-time lows of approximately 23°C. The meteorological year is divided into two parts: a pronounced dry season (approximately from mid-December to the end of April), and a wet season (May to mid-December). On average, only 285 mm of rain falls during the dry season. Relative humidity, soil moisture, air pressure, solar radiation, evapotranspiration, wind speed and direction all show marked wet/dry season differences. On the other hand, temperature varies relatively little throughout the year. Click here for a summary of BCI data.
Data are collected from two locations on the northeast corner of the island: a walk-up tower located within a small catchment known as Lutz, and a small clearing (‘El Claro’) located among several laboratory buildings. A third site, located on the far side of the island from Lutz, is known as the Conrad Stream Weir. This site currently consists of a small V-notch weir and a tipping bucket.
Originally 42m in height, the Lutz tower was increased in mid-October, 2001 to 48m. The tower has been fitted temperature/humidity sensors at 10 m intervals to provide a vertical meteorological transect through the forest canopy. In addition, on the uppermost level of the tower, there are quantum and pyranometer solar radiation sensors, an anemometer and an atmometer (EtGage). The is also a V-notch weir near the base of the tower which measures the run-off from most of the Lutz creek catchment.
The Lutz catchment is probably typical of the many small, steeply-sloped catchments draining away from the center of the island. It is located immediately east of the laboratory clearing. The steeply sloped (20-30°) catchment drains an area of 9.73 ha.  The forest covering the catchment was mostly deforested during the construction of the Panama Canal around the turn of the century, but since then has been allowed to regenerate.
The Conrad catchment is a more gently sloped catchment draining much of the center part of the island, including most of the 50-ha plot. The catchment is approximately 40.2 ha in size. Unlike with the Lutz catchment, the forest covering the catchment was not deforested during the construction of the Panama Canal.
The Clearing is a grass-covered area located near the foundations of several former laboratory buildings. The physical aspects of both the Clearing and the Tower have changed somewhat over time since they were established in 1972. The Clearing has seen a number of cycles of vegetation removal and re-growth in the surrounding area including the recent loss of the nearest large tree . In addition, in the last 6 years two nearby laboratory buildings have been demolished and a large 30m(?) communications tower has been erected. Unfortunately, these changes may have affected the local climate around the Clearing. In the case of the Tower, it is evident that the forest canopy surrounding the Tower has risen, perhaps as much as 5m, since the Tower was erected – with possible measurement implications, especially at the highest levels.  The elevation of this site is 61 m a.m.s.l.
Data are collected using two different methods: electro-mechanical (electronic sensors, data loggers, chart recorders, etc.), and manual (rain gauges, max-min thermometers, sling psychrometers, soil samples, etc.) by a technician. In general, manual measurements have shown themselves to provide the most accurate measurements over the long-term. Where ever possible, parameters are measured both manually and electronically. The only exceptions to this rule are solar radiation (electronic only) and estimated evapotranspiration (manual only). You can see a description of this equipment by clicking here.