Water Storage Capacity (water + storage_capacity)

Distribution by Scientific Domains

Selected Abstracts

Modelling rainfall interception loss in forest restoration trials in Panama

ECOHYDROLOGY, Issue 3 2010
Darryl E. Carlyle-Moses
Abstract A modified Liu analytical model of rainfall interception (Ic) by tree canopies was evaluated using rainfall, throughfall and stemflow data collected from forest restoration trials in the Republic of Panama. The model uses an introduced approach to estimating the water storage capacities of tree boles, which has a more realistic physical basis than earlier iterations of the Liu model. Study species (Acacia mangium, Gliricidia sepium, Guazuma ulmifolia, Ochroma pyramidale, and Pachira quinata) were selected on the basis of differing leaf size and crown characteristics. Significant interspecific differences in both observed and simulated cumulative interception loss were found, with A. mangium intercepting more rainfall than other species. Errors between calculated and modelled cumulative Ic ranged from + 6·3% to + 30·5%, with modelled Ic always being the larger term. During-event evaporation rates from the study trees were positively related to tree height, crown area, and basal diameter. Crown area and the storage capacity of tree boles were negatively correlated. The results of a sensitivity analysis suggested that the modified model was most sensitive to variations in during-event evaporation rate. The implications of the model's sensitivity to during-event evaporation and the importance of this mechanism of interception loss are discussed, while suggestions are provided that may lead to further improvements to the analytical model. Copyright © 2010 John Wiley & Sons, Ltd. [source]

The role of vegetation patterns in structuring runoff and sediment fluxes in drylands

Juan Puigdefábregas
Abstract The dynamics of vegetation-driven spatial heterogeneity (VDSH) and its function in structuring runoff and sediment fluxes have received increased attention from both geomorphological and ecological perspectives, particularly in arid regions with sparse vegetation cover. This paper reviews the recent findings in this area obtained from field evidence and numerical simulation experiments, and outlines their implications for soil erosion assessment. VDSH is often observed at two scales, individual plant clumps and stands of clumps. At the patch scale, the local outcomes of vegetated patches on soil erodibility and hydraulic soil properties are well established. They involve greater water storage capacity as well as increased organic carbon and nutrient inputs. These effects operate together with an enhanced capacity for the interception of water and windborne resources, and an increased biological activity that accelerates breakdown of plant litter and nutrient turnover rates. This suite of relationships, which often involve positive feedback mechanisms, creates vegetated patches that are increasingly different from nearby bare ground areas. By this way a mosaic builds up with bare ground and vegetated patches coupled together, respectively, as sources and sinks of water, sediments and nutrients. At the stand scale within-storm temporal variability of rainfall intensity controls reinfiltration of overland flow and its decay with slope length. At moderate rainfall intensity, this factor interacts with the spatial structure of VDSH and the mechanism of overland flow generation. Reinfiltration is greater in small-grained VDSH and topsoil saturation excess overland flow. Available information shows that VDSH structures of sources and sinks of water and sediments evolve dynamically with hillslope fluxes and tune their spatial configurations to them. Rainfall simulation experiments in large plots show that coarsening VDSH leads to significantly greater erosion rates even under heavy rainfall intensity because of the flow concentration and its velocity increase. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Occurrence, prediction and hydrological effects of water repellency amongst major soil and land-use types in a humid temperate climate

S. H. Doerr
Summary Knowledge of soil water repellency distribution, of factors affecting its occurrence and of its hydrological effects stems primarily from regions with a distinct dry season, whereas comparatively little is known about its occurrence in humid temperate regions such as typified by the UK. To address this research gap, we have examined: (i) water repellency persistence (determined by the water drop penetration time method, WDPT) and degree (determined by the critical surface tension method, CST) for soil samples (0,5, 10,15 and 20,25 cm depth) taken from 41 common soil and land-use types in the humid temperate climate of the UK; (ii) the supposed relationship of soil moisture, textural composition and organic matter content with sample repellency; and (iii) the bulk wetting behaviour of undisturbed surface core samples (0,5 cm depth) over a period of up to 1 week. Repellency was found in surface samples of all major soil textural types amongst most permanently vegetated sites, whereas tilled sites were virtually unaffected. Repellency levels reached those of the most severely affected areas elsewhere in the world, decreased in persistence and degree with depth and showed no consistent relationship with soil textural characteristics, organic matter or soil moisture contents, except that above a water content of c. 28% by volume, repellency was absent. Wetting rate assessments of 100 cm3 intact soil cores using continuous water contact (,20 mm pressure head) over a period of up to 7 days showed that across the whole sample range and irrespective of texture, severe to extreme repellency persistence consistently reduced the maximum water content at any given time to well below that of wettable soils. For slightly to moderately repellent soils the results were more variable and thus hydrological effects of such repellency levels are more difficult to predict. The results imply that: (i) repellency is common for many land-use types with permanent vegetation cover in humid temperate climates irrespective of soil texture; (ii) supposedly influential parameters (texture, organic matter, specific water content) are poor general predictors of water repellency, whereas land use and the moisture content below which repellency can occur seem more reliable; and (iii) infiltration and water storage capacity of very repellent soils are considerably less than for comparable wettable soils. [source]

Rainfall distribution is the main driver of runoff under future CO2 -concentration in a temperate deciduous forest

Abstract Reduced stomatal conductance under elevated CO2 results in increased soil moisture, provided all other factors remain constant. Whether this results in increased runoff critically depends on the interaction of rainfall patterns, soil water storage capacity and plant responses. To test the sensitivity of runoff to these parameters under elevated CO2, we combine transpiration and soil moisture data from the Swiss Canopy Crane FACE experiment (SCC, 14 30,35 m tall deciduous broad-leaved trees under elevated CO2) with 104 years of daily precipitation data from an adjacent weather station to drive a three-layer bucket model (mean yearly precipitation 794 mm). The model adequately predicts the water budget of a temperate deciduous forest and runoff from a nearby gauging station. A simulation run over all 104 years based on measured sap flow responses resulted in only 5.5 mm (2.9%) increased ecosystem runoff under elevated CO2. Out of the 37 986 days (1 January 1901,31 December 2004), only 576 days produce higher runoff in the elevated CO2 scenario. Only 1 out of 17 years produces a CO2 -signal >20 mm a,1, which mostly depends on a few single days when runoff under elevated CO2 exceeds runoff under ambient conditions. The maximum signal for a double preindustrial CO2 -concentration under the past century daily rainfall regime is an additional runoff of 46 mm. More than half of all years produce a signal of <5 mm a,1, because trees consume the ,extra' moisture during prolonged dry weather. Increased runoff under elevated CO2 is nine times more sensitive to variations in rain pattern than to the applied reduction in transpiration under elevated CO2. Thus the key driver of increased runoff under future CO2 -concentration is the day by day rainfall pattern. We argue that increased runoff due to a first-order plant physiological CO2 -effect will be very small (<3%) in a landscape dominated by temperate deciduous forests, and will hardly increase flooding risk in forest catchments. Monthly rainfall sums are unsuitable to realistically model such CO2 effects. These findings may apply to other ecosystems with comparable soil water storage capacity. [source]

Seasonal changes in runoff characteristics on a permafrost watershed in the southern mountainous region of eastern Siberia

Yusuke Yamazaki
Abstract We attempted to clarify the runoff characteristics of a permafrost watershed in the southern mountainous region of eastern Siberia using hydrological and meteorological data obtained by the State Hydrological Institute in Russia from 1976 to 1985. We analysed seasonal changes in the direct runoff ratio and recession gradient during the permafrost thawing period. Thawing depth began to increase from the beginning of May and continued to increase until the end of September, exceeding 150 cm. Annual precipitation and discharge were in the range 525,649 mm and 205,391 mm respectively. The sum of the annual evapotranspiration and changes in water storage ranged from 235 to 365 mm. The mean daily evapotranspiration in June, July, August and September was 1·5 mm day,1, 1·7 mm day,1, 1·5 mm day,1, and 0·5 mm day,1 respectively. The direct runoff ratio was highest in June, decreasing from 0·8 in June to 0·2 in September. The recession gradient also decreased from June to September. Since the frozen soil functioned as an impermeable layer, the soil water storage capacity in the thawing part of the soil, the depth of which changed over time, controlled the runoff characteristics. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Controls on runoff from a partially harvested aspen-forested headwater catchment, Boreal Plain, Canada

K. J. Devito
Abstract The water balance and runoff regime of a 55 ha aspen-forested headwater catchment located on the Boreal Plain, Alberta, Canada (55·1°N, 113·8°W) were determined for 5 years following a partial timber harvest. Variability in precipitation provided the opportunity to contrast catchment water balances in relatively dry (<350 mm year,1), wet (>500 mm year,1), and average precipitation years. In most years, the catchment water balance was dominated by soil water storage, evapotranspiration losses, and vertical recharge. In 1997, despite near-average annual precipitation (486 mm), there was significant runoff (250 mm year,1) with a runoff coefficient of 52%. A wet summer and autumn in the preceding year (1996) and large snow accumulation in the spring (1997) reduced the soil water storage potential, and large runoff occurred in response to a substantial July rainfall event. Maps of the surface saturated areas indicated that runoff was generated from the uplands, ephemeral draws, and valley-bottom wetlands. Following 1997, evapotranspiration exceeded precipitation and large soil water storage potentials developed, resulting in a reduction in surface runoff to 11 mm in 1998, and <2 mm in 1999,2001. During this time, the uplands were hydrologically disconnected from ephemeral draws and valley-bottom wetlands. Interannual variability was influenced by the degree of saturation and connectivity of ephemeral draws and valley wetlands. Variability in runoff from tributaries within the catchment was influenced by the soil water storage capacity as defined by the depth to the confining layer. An analysis of the regional water balance over the past 30 years indicated that the potential to exceed upland soil water storage capacity, to connect uplands to low-lying areas, and to generate significant runoff may only occur about once every 20 years. The spatial and temporal variability of soil water storage capacity in relation to evaporation and precipitation deficits complicates interpretation of forest harvesting studies, and low runoff responses may mask the impacts of harvesting of aspen headwater areas on surface runoff in subhumid climates of the Boreal Plain. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Estimating areal snowmelt infiltration into frozen soils

D. M. Gray
Abstract An algorithm for estimating areal snowmelt infiltration into frozen soils is developed. Frozen soils are grouped into classes according to surface entry condition as: (a) Restricted,water entry is impeded by surface conditions, (b) Limited,capillary flow predominates and water entry is influenced primarily by soil physical properties, and (c) Unlimited,gravity flow predominates and most of the meltwater infiltrates. For Limited soils cumulative infiltration over time is estimated by a parametric equation from surface saturation, initial soil moisture content (water + ice), initial soil temperature and infiltration opportunity time. Total infiltration into Unlimited and Limited soils is constrained by the available water storage capacity. This constraint is also used to determine when Limited soils have thawed. The minimum spatial scale of the infiltration model is established for Limited soils by the variabilities in surface saturation, snow water equivalent, soil infiltrability, soil moisture (water + ice) and depth of soil freezing. Since snowmelt infiltration is influenced by other processes and factors that affect snow ablation, it is assumed that the infiltrability spatial scale should be consistent with the scales used to describe these variables. For open, northern, cold regions the following order in spatial scales is hypothesized: frozen ground , snowmelt , snow water equivalent , frozen soil infiltrability , soil moisture (water + ice) and snow water. For mesoscale application of the infiltration model it is recommended that the infiltrability scale be taken equal to the scale used to describe the areal extent and distribution of the water equivalent of the snowcover that covers frozen ground. Scaling the infiltrability of frozen soils in this manner allows one to exploit established landscape-stratification methodology used to derive snow accumulation means and distribution. Scaling of soil infiltrability at small scales (microscale) is complicated and requires information on the association(s) between the spatial distributions of soil moisture (water + ice) and snow water. A flow chart of the algorithm is presented. Copyright © 2001 John Wiley & Sons, Ltd. [source]

A method for improving predictions of bed-load discharges to reservoirs

Vicente L. Lopes
Abstract Effective management options for mitigating the loss of reservoir water storage capacity to sedimentation depend on improved predictions of bed-load discharges into the reservoirs. Most predictions of bed-load discharges, however, are based on the assumption that the rates of bed-load sediment availability equal the transport capacity of the flow, ignoring the spatio-temporal variability of the sediment supply. This paper develops a semiquantitative method to characterize bed-load sediment transport in alluvial channels, assuming a channel reach is non-supply limited when the bed-load discharge of a given sediment particle-size class is functionally related to the energy that is available to transport that fraction of the total bed-load. The method was applied to 22 alluvial stream channels in the USA to determine whether a channel reach had a supply-limited or non-supply-limited bed-load transport regime. The non-supply-limited transport regime was further subdivided into two groups on the basis of statistical tests. The results indicated the pattern of bed-load sediment transport in alluvial channels depends on the complete spectrum of sediment particle sizes available for transport rather than individual particle-size fractions represented by one characteristic particle size. The application of the method developed in this paper should assist reservoir managers in selecting bed-load sediment transport equations to improve predictions of bed-load discharge in alluvial streams, thereby significantly increasing the efficiency of management options for maintaining the storage capacity of waterbodies. [source]

Observations of debris-rich naled associated with a major glacier surge event, Disko Island, West Greenland

Jacob Clement Yde
Abstract Glacier naled formation is associated with surge-type glaciers both during active surging and in quiescence. During the 1995,98 surge of Kuannersuit Glacier, Disko Island, West Greenland, turbid winter runoff produced an extensive naled accretion with a distinct debris-rich stratification. After surge termination the summer occurrence of naledi gradually decreased and disappeared within 5 years. The fine-grained debris was deposited on top of outwash deposits on bars and banks. Observations at the margin of surrounding glaciers revealed that only surge-type glaciers in their quiescent phase had proglacial naled assemblages, although these lacked incorporated debris. This indicates that surge-type glaciers have a significant impact on the occurrence of naledi primarily because their subglacial thermal conditions and water storage capacity allow significant winter runoff implying high hydraulic pressure on proglacial outwash plains. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Ground-penetrating radar survey over bronze age circular monuments on a sandy soil, complemented with electromagnetic induction and fluxgate gradiometer data

L. Verdonck
Abstract This paper presents a ground-penetrating radar (GPR) survey over two circular structures originally surrounding Bronze Age burial mounds at the site of Koekelare (western Belgium). The region is characterized by sandy soils. Their low water storage capacity and the consequent moisture contrasts in dry summers played an important role in the detection of over 1000 Bronze Age funeral monuments through aerial archaeology in the past few decades. At Koekelare, low attenuation of GPR waves resulted in the detection of a double and single circular ditch. A fluxgate gradiometer survey and electromagnetic induction (EMI) measurements did not clearly reveal the ditches. For the GPR wave velocity analysis, constant velocity migration tests were combined with time-domain reflectometry (TDR). The TDR measurements were made at different depths within the ditches and in the adjacent undisturbed soil, so that the differences in the physical soil parameters could be assessed. At a depth of approximately 0.45 to 0.8,m, the relatively homogeneous ditch fill produces few GPR reflections compared with the undisturbed soil, and is visible as a weak negative anomaly on the horizontal slices. At this depth, the grey or brownish black ditch fill was found in augering samples, clearly distinguishable from the yellowish brown sandy soil outside the ditches. The transition between the ditch and the underlying soil caused a gradual reflection of radar energy at a depth of approximately 0.8 to 1.2,m, although TDR showed no marked differences in relative permittivity between the ditches and the surrounding soil, and no clear steps as a function of depth. Copyright © 2009 John Wiley & Sons, Ltd. [source]