Hydrological connectivity of alluvial Andean valleys: a groundwater/surface-water interaction case study in Ecuador

Feyen

et al. 2017

Hydrological Processes

To improve the current knowledge of the rainfall–runoff phenomena of tropical montane catchments, we explored the usefulness of several hydrological indicators on a nested cloud forest catchment (76.9 km2). The used metrics belong to 5 categories: baseflow mean transit time, physicochemical properties of stream water, land cover, topographic, and hydrometric parameters. We applied diverse statistical techniques for data analysis and to contrast findings. Multiple regression analysis showed that mean transit times of base flow could be efficiently predicted by sodium concentrations (higher during baseflows) and temperatures of stream water, indicating a major influence of geomorphology rather than topographic or land cover characteristics. Principal component analysis revealed that no specific subset of catchment indicators could be identified as prevailing descriptors for all catchments. The agglomerative hierarchical clustering analysis provided concomitant results, implying larger levels of dissimilarity between smaller subcatchments than between larger ones. Overall, results point out an intricate interdependence of diverse processes at surface and subsurface level indicating a high level of heterogeneity. Disregarding heterogeneity of nested or paired catchments could lead to incomplete or misleading conclusions, especially in tropical mountain regions where pronounced spatial and temporal gradients are present.

Section: Discussionsupporting

confidence: 61%

Multicriteria assessment of water dynamics reveals subcatchment variability in a seemingly homogeneous tropical cloud forest catchment

Feyen

et al. 2017

Hydrological Processes

“…Walker et al () estimated groundwater recharge in the humid highlands from 45 to 814 mm/year depending on the type of method used. Using the appropriate method for determining recharge and groundwater availability is therefore crucial (Guzman, Anibas, Batelaan, Huysmans, & Wyseure, ; Walraevens et al, ).…”

Section: Introductionmentioning

confidence: 99%

Establishing irrigation potential of a hillside aquifer in the African highlands

Tilahun

Yilak

Schmitter³

et al. 2020

Hydrological Processes

Feeding 9 billion people in 2050 will require sustainable development of all water resources, both surface and subsurface. Yet, little is known about the irrigation potential of hillside shallow aquifers in many highland settings in sub-Saharan Africa that are being considered for providing irrigation water during the dry monsoon phase for smallholder farmers. Information on the shallow groundwater being available in space and time on sloping lands might aid in increasing food production in the dry monsoon phase. Therefore, the research objective of this work is to estimate potential groundwater storage as a potential source of irrigation water for hillside aquifers where lateral subsurface flow is dominant. The research was carried out in the Robit Bata experimental watershed in the Lake Tana basin which is typical of many undulating watersheds in the Ethiopian highlands. Farmers have excavated more than 300 hand dug wells for irrigation. We used 42 of these wells to monitor water table fluctuation from April 16, 2014 to December 2015. Precipitation and runoff data were recorded for the same period. The temporal groundwater storage was estimated using two methods: one based on the water balance with rainfall as input and baseflow and evaporative losses leaving the watershed as outputs; the second based on the observed rise and fall of water levels in wells. We found that maximum groundwater storage was at the end of the rain phase in September after which it decreased linearly until the middle of December due to short groundwater retention times. In the remaining part of the dry season period, only wells located close to faults contained water. Thus, without additional water sources, sloping lands can only be used for significant irrigation inputs during the first 3 months out of the 8 months long dry season. K E Y W O R D SEthiopia, groundwater, highlands, irrigation, Lake Tana, water budget, water storage, water table fluctuation method

“…The measurements of the solar radiation by the meteorological stations in our experimental catchments were not consistent and considered to be unreliable. Therefore, the solar radiation was estimated by the Hargreaves-Samani equation (Hargreaves and Samani, 1985) using the daily maximum and minimum air temperature:…”

Section: The Potential Evapotranspirationmentioning

confidence: 99%

“…Where R s is the solar radiation [MJ m −2 d −1 ], R a is the extraterrestrial solar radiation [MJ m −2 d −1 ], c is an empirical co- According to Hargreaves and Samani (1985) "c" has a value of 0.17 for inland areas.…”

Section: The Potential Evapotranspirationmentioning

confidence: 99%

Analysis of the drought resilience of Andosols on southern Ecuadorian Andean páramos

Iñiguez¹,

Morales²,

Cisneros³

et al. 2015

Preprint

The Neotropical Andean grasslands above 3500 m a.s.l., known as páramo, offer remarkable ecological services for the Andean region. The most important of these is the water supply of excellent quality to many cities and villages in the inter-Andean valleys and along the coast. The páramo ecosystem and especially its soils are under constant and increased threat by human activities and climate change. In this study, the recovery speed of the páramo soils after drought periods are analysed. The observation period includes the droughts of 2009, 2010, 2011, and 2012 together with intermediate wet periods. Two experimental catchments -one with and one without páramo -were investigated. The Probability Distributed Moisture (PDM) model was calibrated and validated in both catchments. Drought periods and its characteristics were identified and quantified by a threshold level approach and complemented by means of a drought propagation analysis. At the plot scale in the páramo region, the soil water content measured by time domain reflectometry (TDR) probes dropped from a normal value of about 0.84 to ∼ 0.60 cm 3 cm −3 , while the recovery time was 2-3 months. This did not occur at lower altitudes (Cumbe) where the soils are mineral. Although the soil moisture depletion observed in these soils was similar to that of the Andosols (27 %), decreasing from a normal value of about 0.54 to ∼ 0.39 cm 3 cm −3 , the recovery was much slower and took about 8 months for the drought in 2010. At the catchment scale, however, the soil water storage simulated by the PDM model and the drought analysis was not as pronounced. Soil moisture droughts occurred mainly in the dry season in both catchments. The deficit for all cases is small and progres-sively reduced during the wet season. Vegetation stress periods correspond mainly to the months of September, October and November, which coincides with the dry season. The maximum number of consecutive dry days were reached during the drought of 2009 and 2010 (19 and 22 days), which can be considered to be a long period in the páramo. The main factor in the hydrological response of these experimental catchments is the precipitation relative to the potential evapotranspiration. As the soils never became extremely dry nor close to the wilting point, the soil water storage capacity had a secondary influence.