The effect of land‐use changes on the hydrological behaviour of Histic Andosols in south Ecuador

Abstract

Abstract:The south Ecuadorian Andean mountain belt between 3500 and 4500 m altitude is covered by a highly endemic and fragile ecosystem called páramo. The Histic Andosols covering this region have highly developed hydric properties and exert a key function in the hydrological regulation of the páramo ecosystem. Unlike most Andosols, their extreme water retention capacity is not due to the presence of typical minerals such as allophane or imogolite. Although these minerals are virtually absent, the large organic carbon content, due to organometallic complexation, gives rise to similar properties. The water content at 1500 kPa can exceed 2000 g kg 1 , and the high hydraulic conductivity at saturation (about 15 mm h 1 ) drops sharply when low suction is applied. The three methods applied, i.e. the inverted auger hole, the tension infiltrometer and the constant-head permeameter method, give very similar results. The páramo is characterized by a slow hydrological response and a good water regulation, caused by the combination of a high water storage capacity and high conductivity. The wide pore size distribution of the organometallic complexes results in a water retention curve that differs significantly from the classic Mualem-Van Genuchten description, but can better be described with a simple linear or semilogarithmic model. The soils investigated are very prone to irreversible structural changes caused by land-use changes. The conversion of natural land for cultivation has a large impact on the hydrological function of the region. The water storage capacity increases by 5 to 30%, and the hydraulic conductivity is 31% higher in cultivated catchments. These changes are related to a larger peak flow, a smaller base flow and generally a smaller discharge buffering capacity, despite the higher storage capacity.

Icelandic Inland Wetlands: Characteristics and Extent of Draining

“…The mixture of poorly crystalline basaltic volcanic materials and peat, which dominates Icelandic wetland soils, is uncommon in the world, judging from our literature search. They differ from the paramo Histic Andosols of Ecuador (Buytaert et al 2005(Buytaert et al , 2007 and the Azores (Madeira et al 2007) in having a lower content of metal-humus complexes and a higher proportion of vitric materials deposited by continuous re-distribution of volcanic ash materials. The Icelandic wetland soils rarely exhibit hydric soil properties (>100 % water content at 15 bar tension) in contrast to more developed Hydric Andosols of warmer climates.…”

Regionalization as a learning process

“…The geology of all catchments consists of Cretaceous and early Tertiary lavas and andesitic volcanoclastic deposits, shaped and compacted by glacier activity during the last ice age [Coltorti and Ollier, 2000;Hungerbühler et al, 2002]. The hydraulic conductivity of the bedrock is low, particularly compared to the hydraulic conductivity of the thin layer of volcanic ashes that constitute the soil layer [Buytaert et al, 2005]. On average, the soil layer is about 80 cm thick, with some bedrock outcroppings at convex locations and hilltops [Buytaert et al, 2006c].…”

“…[34] The absence of a dry season [Buytaert et al, 2006b], and the marked drop of soil hydraulic conductivity in nonsaturated conditions result in continuously wet soils (>60 vol% [Buytaert et al, 2005]). Field research has shown that also in dry periods a saturated soil layer exists above the bedrock, even on steep slopes [Buytaert et al, 2005].…”

Streamflow forecasts from WRF precipitation for flood early warning in mountain tropical areas

“…This corresponds to a páramo, which is a tropical high-mountain ecosystem, characterised by soils with a high water storage capacity and high conductivity. The hydrologic behaviour of páramo is complex, and there are still major gaps in knowledge (Sevink, 2011;Reyes, 2014;Buytaert et al, 2005Buytaert et al, , 2006. Additionally, hydrometeorological data are scarce.…”