Spatial prediction of stream physicochemical parameters for the Napo River Basin, Ecuador

Abstract

Major threats to freshwater ecosystems in the Andean-Amazon region include agriculture, point and nonpoint source pollution, hydroelectric dams, oil extraction, mining and road building, yet little is known about the baseline values and current state of rivers and streams, or how expanding urban, industrial and agricultural activities could affect and change these freshwater ecosystems and their diversity. Therefore, there is a need to understand physicochemical parameters at the basin scale in many large river systems in the Andean-Amazon such as the Napo River, a world biodiversity hotspot. Establishing baselines for these parameters under less developed conditions will be impossible after development in the watersheds increases and hydroelectric projects reach completion. In addition to collecting data to fill in information gaps in geology, vegetation, disturbance, and other parameters that influence water quality, it is important to use existing data in the Napo to predict chemical parameters throughout the watershed to set a baseline from which deviations from development and climate change can be assessed and to guide data collection efforts. In this study, we provide the first basin-wide estimates of physicochemical parameters (pH, conductivity, dissolved oxygen and temperature) for the entire Napo River Basin using a recently developed geostatistical technique called top kriging. Basin-wide predictions aligned well with observed values and a model validation test showed a strong goodness-of-fit for parameter estimates. Furthermore, our predictions aligned well with observed values from independent datasets from the Napo Basin. These predictions could be useful in developing water quality reference baselines for the basin and for monitoring relative changes to parameters, assist in the identification of priority areas within the basin for management and conservation efforts, direct future research, and be applied in other data-scarce basins in remote regions worldwide.

Variations in Benthic Macroinvertebrate Communities and Biological Quality in the Aguarico and Coca River Basins in the Ecuadorian Amazon

“…The impact of the latter type of stressors is very severe and interrupts the dynamics and ecological functions that normally are given by the site-specific conditions, the seasonal fluctuations of the physical-chemical variables, or the temporal patterns of rainfall, which determine the composition of aquatic invertebrate communities. Instead, biological communities decline dramatically in terms of abundance and diversity, and, in some cases, they even disappear from the impacted systems [9,54,61]. Comparable findings are reported in several similar studies in other tropical regions (e.g., [87][88][89][90][91]).…”

“…Both the CRB and ARB discharge the water into the Napo River within the Ecuadorian territory before joining the Amazon River. The highland rivers from the Napo basin (such as Coca, Tiputini, Yasuní, Aguarico) are known as "aguas blancas" (white waters) [54]. The whitewater systems originate in the Andean snowmelts and high altitude paramo grasslands at elevations over 4000 m, and have a muddy colour caused by drainage carrying heavy sediment loads from eroding uplands [57].…”

“…The climate here is characterized by heavy rainfall throughout the year. The average annual precipitation during the hydrological year is around 3500 mm, with an average of 19 rainy days per month, although it is possible to distinguish, slightly, a rainy season that occurs from April to July from a less marked dry season from November to February [54]. Beyond oil-related activities, other types of human activity are present in these basins: dams, mining, agriculture, livestock, and fishing.…”

Validating anthropogenic threat maps as a tool for assessing river ecological integrity in Andean–Amazon basins

“…Then, we estimated the deviations from human development by calculating the absolute difference between observed values and references values. These reference values were obtained from Alexiades et al (2019).…”

Challenges to Water Management in Ecuador: Legal Authorization, Quality Parameters, and Socio-Political Responses

“…Similarly, a study of the Salado Estuary found bioaccumulation of Hg in mussels and poor quality parameters such as low dissolved oxygen (DO) to be indicative of limited biodiversity and diminished body sizes among local fish populations [56]. Nevertheless, it is important to recognize that fluctuations in pH, temperature, DO, and other parameters are also informed by natural and seasonal variation [57]. For example, in a study of the Napo River Basin, these parameters varied both spatially and temporally as a result of geographical and seasonal changes [57].…”