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- Bishop, Kevin, et al.
(author)
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Water storage in a till catchment. II : Implications of transmissivity feedback for flow paths and turnover times
- 2011
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In: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 25:25, s. 3950-3959
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Journal article (peer-reviewed)abstract
- This paper explores the flow paths and turnover times within a catchment characterized by the transmissivity feedback mechanism where there is a strong increase in the saturated hydraulic conductivity towards the soil surface and precipitation inputs saturate progressively more superficial layers of the soil profile. The analysis is facilitated by the correlation between catchment water storage and groundwater levels, which made it possible to model the daily spatial distribution of water storage, both vertically in different soil horizons and horizontally across a 6300-m2 till catchment. Soil properties and episodic precipitation input dynamics, combined with the influence of topographic features, concentrate flow in the horizontal, vertical, and temporal dimensions. Within the soil profile, there was a vertical concentration of lateral flow to superficial soil horizons (upper 30?cm of the soil), where much of the annual flow occurred during runoff episodes. Overland flow from a limited portion of the catchment can contribute to peak flows but is not a necessary condition for runoff episodes. The spatial concentration of flow, and the episodic nature of runoff events, resulted in a strong and spatially structured differentiation of local flow velocities within the catchment. There were large differences in the time spent by the laterally flowing water at different depths, with turnover times of lateral flow across a 1-m-wide soil pedon ranging from under 1?h at 10- to 20-cm depth to a month at 70- to 80-cm depth. In many regards, the hydrology of this catchment appears typical of the hydrology in till soils, which are widespread in Fenno-Scandia. Copyright (c) 2011 John Wiley & Sons, Ltd.
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- Seibert, J., 1968-, et al.
(author)
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Water storage in a till catchment. I : Distributed modelling and relationship to runoff
- 2011
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In: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 25:25, s. 3937-3949
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Journal article (peer-reviewed)abstract
- Although water storage is an important variable to understand the hydrological functioning of a catchment, it is challenging to estimate the total water storage in a catchment. Catchment water storage can be estimated on the basis of water balance, but this approach is prone to errors in the different water balance terms. Here, an approach is presented to estimate the daily dynamics of catchment-wide soil water and groundwater storage on the basis of groundwater-level observations, soil properties and an assumption of hydrological equilibrium above the water table. This approach was applied to a 6300-m2 till catchment in Southwest Sweden. The predicted mean catchment water storage between April 1991 and June 1992 was 210mm and ranged from 190 to 260mm. The estimated water storage followed runoff rates closely especially during recession periods. On average, 79% of the water storage was held in the unsaturated zone, and the remaining 21% was groundwater, but this proportion varied strongly with runoff and total storage. During dry conditions, unsaturated storage accounted for at maximum 95% of the water storage; during wet conditions, this number dropped to 40%. Copyright (c) 2011 John Wiley & Sons, Ltd.
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- Soulsby, C., et al.
(author)
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Catchment-scale estimates of flow path partitioning and water storage based on transit time and runoff modelling
- 2011
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In: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 25:25, s. 3960-3976
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Journal article (peer-reviewed)abstract
- Tracer-derived mean transit times (MTT) and rainfallrunoff modelling were used to explore stream flow generation in 14 Scottish catchments. Both approaches conceptualise the partitioning, storage, and release of water at the catchment scale. The study catchments were predominantly upland and ranged from 0.5 to 1800?km2. Lumped convolution integral models using tracer inputoutput relationships generally provided well-constrained MTT estimates using a gamma function as the transit time distribution. These ranged from 60?days to >10?years and are mainly controlled by catchment soil cover and drainage density. The HBV model was calibrated using upper and lower storage layers to conceptualise rapidly responding near-surface flow paths and slower groundwater contributions to runoff. Calibrated parameters that regulate groundwater recharge and partitioning between the two storages were reasonably well-identified and correlations with MTTs. The most clearly identified parameters and those with the strongest correlations with MTT and landscape controls (particularly soil cover) were the recession coefficients which control the release of water from the upper and lower storage layers. There was also strong correlation between the dynamic storage estimated by HBV and the total catchment storage inferred by tracer damping, although the latter was usually two orders of magnitude greater. This is explained by the different storages estimated: while the total storage inferred by tracers also includes the passive storage involved in mixing, the model estimates dynamic storage from water balance considerations. The former can be interpreted as relating to total porosity, whereas the latter rather corresponds to the drainable porosity. As MTTs for Scottish the uplands can be estimated from catchment characteristics, landscape analysis can be used to constrain sensitive model parameters when modelling in ungauged basins. Furthermore, the dynamic storage inferred by HBV may also be used to provide a first approximation of minimum total catchment storage. Copyright (c) 2011 John Wiley & Sons, Ltd.
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