Regionalization of land-use impacts on streamflow using a network of paired catchments
Author: Boris F. Ochoa-Tocachi1,2,3, Wouter Buytaert1,3, and Bert De Bie `vre2,3,4
Published online: 3 SEP 2016
Quantifying the impact of land use and cover (LUC) change on catchment hydrological response is essential for land-use planning and management. Yet hydrologists are often not able to present consistent and reliable evidence to support such decision-making. The issue tends to be twofold: a scarcity of relevant observations, and the difﬁculty of regionalizing any existing observations. This study explores the potential of a paired catchment monitoring network to provide statistically robust, regionalized predictions of LUC change impact in an environment of high hydrological variability. We test the importance of LUC variables to explain hydrological responses and to improve regionalized predictions using 24 catchments distributed along the Tropical Andes. For this, we calculate ﬁrst 50 physical catchment properties, and then select a subset based on correlation analysis. The reduced set is subsequently used to regionalize a selection of hydrological indices using multiple linear regression. Contrary to earlier studies, we ﬁnd that incorporating LUC variables in the regional model structures increases signiﬁcantly regression performance and predictive capacity for 66% of the indices. For the runoff ratio, baseﬂow index, and slope of the ﬂow duration curve, the mean absolute error reduces by 53% and the variance of the residuals by 79%, on average. We attribute the explanatory capacity of LUC in the regional model to the pairwise monitoring setup, which increases the contrast of the land-use signal in the data set. As such, it may be a useful strategy to optimize data collection to support watershed management practices and improve decision-making in data-scarce regions.
Impacts of land use on the hydrological response of tropical Andean catchments
Author: Boris F. Ochoa-Tocachi, Wouter Buytaert, Bert De Bièvre, Rolando Célleri, Patricio Crespo, Marcos Villacís, Carlos A. Llerena, Luis Acosta, Mauricio Villazón, Mario Guallpa, Junior Gil-Ríos, Paola Fuentes, Dimas Olaya, Paúl Viñas, Gerver Rojas10 and Sandro Arias.
Published online: Received 30 November 2015; Accepted 26 July 2016.
Keywords: hydrological response; land use; LUCC; Andes; páramo; puna; jalca; indices
Changes in land use and land cover are major drivers of hydrological alteration in the tropical Andes. However, quantifying their impacts is fraught with difﬁculties because of the extreme diversity in meteorological boundary conditions, which contrasts strongly with the lack of knowledge about local hydrological processes. Although local studies have reduced data scarcity in certain regions, the complexity of the tropical Andes poses a big challenge to regional hydrological prediction. This study analyses data generated from a participatory monitoring network of 25 headwater catchments covering three of the major Andean biomes (páramo, jalca and puna) and links their hydrological responses to main types of human interventions (cultivation, afforestation and grazing). A paired catchment setup was implemented to evaluate the impacts of change using a ‘trading spacefor-time’ approach. Catchments were selected based on regional representativeness and contrasting land use types. Precipitation and discharge have been monitored and analysed at high temporal resolution for a time period between 1 and 5years. The observed catchment responses clearly reﬂect the extraordinarily wide spectrum of hydrological processes of the tropical Andes. They range from perennially humid páramos in Ecuador and northern Peru with extremely large speciﬁc discharge and baseﬂows, to highly seasonal, ﬂashy catchments in the drier punas of southern Peru and Bolivia. The impacts of land use are similarly diverse and their magnitudes are a function of catchment properties, original and replacement vegetation and management type. Cultivation and afforestation consistently affect the entire range of discharges, particularly low ﬂows. The impacts of grazing are more variable but have the largest effect on the catchment hydrological regulation. Overall, anthropogenic interventions result in increased streamﬂow variability and signiﬁcant reductions in catchment regulation capacity and water yield, irrespective of the hydrological properties of the original biome. Copyright © 2016 The Authors. Hydrological Processes. Published by John Wiley & Sons Ltd.
High-resolution hydrometeorological data from a network of headwater catchments in the tropical Andes
Author: Boris F. Ochoa-Tocachi, Wouter Buytaert, Javier Antiporta, Luis Acosta, Juan D. Bardales, Rolando Célleri, Patricio Crespo, Paola Fuentes, Junior Gil-Ríos, Mario Guallpa, Carlos Llerena, Dimas Olaya2, Pablo Pardo, Gerver Rojas, Marcos Villacís, Mauricio Villazón, Paúl Viñas & Bert De Bièvre.
Published: 3 July 2018
This article presents a hydrometeorological dataset from a network of paired instrumented catchments, obtained by participatory monitoring through a partnership of academic and non-governmental institutions.The network consists of 28 headwater catchments (o20km2) covering three major biomes in 9 locations of the tropical Andes.The data consist of precipitation event records at 0.254mm resolution or ﬁner, water level and streamﬂow time series at 5min intervals, data aggregations at hourly and daily scale, a set of hydrological indices derived from the daily time series, and catchment physiographic descriptors. The catchment network is designed to characterise the impacts of land-use and watershed interventions on the catchment hydrological response, with each catchment representing a typical land use and land cover practice within its location. As such, it aims to support evidence-based decision making on land management, in particular evaluating the effectiveness of catchment interventions, for which hydrometeorological data scarcity is a major bottleneck. The data will also be useful for broader research on Andean ecosystems, and their hydrology and meteorology.
The effects of afforestation and cultivation on water yield in the Andean páramo
Author: Wouter Buytaert a,b, Vicente Iñiguez b, Bert De Bie`vre c
Keywords: Hydrological response; Afforestation; Pinus patula; Water yield; Páramo; Flow duration curves
Over the last decades, the Andean highlands of Ecuador have been characterised by intense afforestation efforts, in order to increase the
economic return of less viable agricultural areas, reduce erosion and, more recently, to sequestrate atmospheric carbon. Afforestation with Pinus
species is widespread in the high altitudinal grasslands known as páramos. The impact of Pinus patula afforestation on the water yield is studied
and compared to the more common practice of intensive grazing and potato cultivation in four microcatchments in the Paute river basin in south
Ecuador. Two catchments are covered with natural grassland vegetation, one is converted to pine forest, and one is drained, partly intensively
grazed, and partly cultivated with potatoes. The results indicate that afforestation with P. patula reduces the water yield by about 50%, or an average
of 242 mm year1. The water yield of the cultivated catchment is very similar to that of the natural catchments, but analysis of the flow duration
curves suggests a faster response and a loss of base flow. These effects may have important implications for a sustainable management of the
pa´ramo ecosystem, given that the páramo is the major water supplier for the Andean highlands.