Methods

The riparian zone of the Quebrada Chires varies significantly over the length of the river. To determine how the surrounding vegetation may affect river dynamics, two sample sites were selected.

Site One - the control site, and was surrounded by secondary rainforest.

Site Two - the base of three agricultural fields which had been clear-cut and served as grazing lands for cattle approximately 1 km down-river from the forested site.

Sample Site Regulations

Each sampling zone was 12 meters in length and varied in width based on precipitation conditions. All data was collected three times in varying precipitation conditions. During the rainy season, rains generally occur daily in the early afternoon. Over the course of two weeks, we measured river conditions when (1) rains had occurred the previous day (i.e. the last 24 hours), (2) no precipitation had occurred in the previous 24 hours and (3) during heavy rainfall when precipitation had begun approximately one half hour prior to data collection.

Site 2 - Proof of pasture lands

River depth and width

The depth of the river was measured in three places at each site, every 0.5 meters to the nearest hundredth of a cm. The width of the river was also calculated during the time the depth was measured at each of the three cross-sections.

1st. Taken at the uppermost portion of the 12 meter sampling zone.

2nd. 6 meters down-river

3rd. At the base of the 12 meter stretch.

During the period of heavy rainfall, the depth of the river was measured only at the uppermost stretch of the 12 meter sampling zone.

River flow

The velocity of the river flow was also measured during the three varying precipitation conditions.

At each site, we measured the time it took a floating object (ping pong ball) to travel the length of the 12 meter sampling zone.
This process was repeated five times at each site, in each condition.
Each trial was timed by two observers, and the average time was taken for each of the five trials.
In the event of severe variation (+/- 30 seconds) an additional five trials were conducted and averaged into the times measured, making a total of ten trials for that site during that particular precipitation condition.