Browsing by Author "Mora, Diego"

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Complex land cover change, water and sediment yield in a degraded Andean environment
(2012-11-23) Molina, Armando; Vanacker, Veerle; Balthazar, Vincent; Mora, Diego; Govers, Gerard
Rapid land use/-cover change has increasingly transformed the hydrological functioning of tropical Andean ecosystems. The hydrological response to forest cover change strongly depends on the initial state of the ecosystem. Relatively little is known about human-disturbed ecosystems where forest plantations have been established on highly degraded land. In this paper, we analyze the impact of forest change on water and sediment fluxes for a highly degraded Andean catchment. Different pathways of land cover change (1963–2007) are observed in the Jadan catchment, with deforestation taking place in remote uplands and recovery and reforestation in the middle and lower parts where agricultural and bare lands are prevalent. Time series analyses of streamflow and rainfall data (1979/1982–2005/2007) show significant shifts in the distribution of rainfall and flow data. Changes in discharge are not resulting from changes in precipitation, as the direction of change is opposite. The removal of native forest for rangeland or croplands (by −20 km2) is likely to have contributed to the increase in total annual water yield, through an increase in annual baseflow by 25 mm. The observed changes in peakflow are important as the 1st percentile highest flow rates were 54% lower, while the 1st percentile rainfall amounts increased by 52%. The observed decrease in peakflow cannot be explained by clearcut of native forest, but is likely to be related to reforestation of degraded lands as well as spontaneous recovery of vegetation on remaining grazing lands. Over the same time period, a major decrease in specific sediment yields and suspended sediment loads was observed. Although deforestation in the upper parts led to increased landslide activity, this change is not reflected in an increased sediment yield. Small upland rivers are often nearly completely blocked by landslide material, thereby reducing their potential to transport sediment. In contrast, the reduction in estimated erosion is likely to be caused by the reduction of the degraded areas in areal extent as well as to the (partial) recovery of the vegetation in these areas.
Decadal oscillations in rainfall and air temperature in the Paute river basin-southern andes of Ecuador
(2012-04) Mora, Diego; Willems, Patrick
In the Andes environment, rainfall and temperature can be extremely variable in space and time. The determination of climate variability and climate change needs a special assessment for water management. This paper examines the anomalies of observed monthly rainfall and temperature data from 25 to 16 stations, respectively, from the early 1960s to the 1990s. The stations are located in the Rio Paute Basin in the Ecuador’s Southern Andes. All stations are within the elevation band 1,800 and 4,200 m a.s.l. and affected by the Tropical Pacific, Amazon, and Tropical Atlantic climate. Anomalies in quantiles were determined for each station and their significance tested. In addition, their correlations with different external climatic influences were studied for anomalies in annual and 3-month seasonal block periods. The results show similar temperature variations for the entire region, which are highly influenced by the El Niño–Southern Oscillation, especially during the December–February season. During June–August, the correlation is weaker showing the influence of other climate factors. Higher temperature anomalies are found at the high elevation sites while at deep valley sites the anomalies are less significant. Rainfall variations depend, in addition to elevation, on additional factors such as the aspect orientation, slope, and hydrological regime. The highest and most significant rainfall anomalies are found in the eastern sites.