Small Experimental Basin Research Articles

Experimental Studies of the Resistance of Transport Ships at Moving in Composite Broken Ice

Arctic ships move in broken ice most of the time. Therefore, forecasting the ice performance of ships when moving in a channel behind an icebreaker or in natural broken ice is relevant at the design stage. For this, theoretical and experimental studies of the movement of various models of ships in a small experimental basin were carried out. The process of modeling and testing of models of active ice navigation ships in a composite ice model is described. Test results and formulas for assessing ice resistance are given. They are derived from the analysis of model tests. Conclusions about the possibility of carrying out and obtaining reliable results of the experiment in small experimental pools are made. The resistance when moving ships in a wide ice channel does not differ from the resistance when moving ships in a field of broken ice. The jamming of ice floes between the edges of the channel and the side occurs when ships move in a narrow channel. Consequently, the “buffering effect” occurs and the resistance increases significantly.

Streamflow response to headwater reforestation in the Ganaraska River basin, southern Ontario, Canada

AbstractIncreased attention is being paid to the role of reforestation in strategies for sustainable forest management, landscape restoration and carbon sequestration. Reforestation of drainage basins is generally assumed to reduce annual streamflow as well as peak and low flows. However, most studies of reforestation effects on streamflow have been conducted on small experimental basins, and the applicability of their results to larger basins is unclear. This study revisits an earlier examination of streamflow response to headwater reforestation in a 267 km2 basin (Ganaraska River) in southern Ontario, Canada for 1945–2007. Forest cover in the basin headwaters increased from 13 km2 in 1945 to 31 km2 by 1990, with most of this change between 1950 and 1965. Streamflow metrics from the reforested basin and two headwater sub‐basins were compared to those from a nearby basin and sub‐basin of similar size and physiography to the Ganaraska basins but without extensive headwater reforestation. No temporal trends were found for inter‐basin differences in annual runoff or runoff ratios for the entire Ganaraska basin or its largest sub‐basin; however, reforestation appears to have reduced several metrics of peak streamflow at the basin and sub‐basin scale. Relationships between high flows classified according to generating event type and the associated precipitation depth suggest that expansion of forest cover in the Ganaraska River basin (GRB) and associated changes in microclimatic conditions have reduced the potential for frozen soil to generate surface runoff and high flows in response to rain‐on‐snow during spring snowmelt. This was accompanied by increased low flows from the GRB and its sub‐basins from 1960 to 2007 relative to the control basin, suggesting that the expanded forest cover has enhanced groundwater recharge by prolonging spring snowmelt and promoting infiltration of rainfall and snowmelt inputs relative to non‐forested areas. Some discrepancies between these results and those of other studies of streamflow response to reforestation may be attributed to the relatively large size of the GRB and the limited extent of reforestation. Nevertheless, the results highlight the importance of considering how reforestation may affect key hydrologic processes in a given landscape when predicting the resulting streamflow response. Copyright © 2011 John Wiley & Sons, Ltd.

Visual observation of erosion processes on the Black Marl badlands in the southern Alps, France

Abstract To clarify the erosion processes on a marly bare slope in the southern Alps, the erosion processes on a steep and erodible slope composed of Black Marls formations were observed using a time-lapse video camera. The observations revealed that miniature debris flows (MDFs) occurred at the time of the rainfall–runoff event during which the most severe erosion took place over the 3 month observation period. Analysing the camera images, we show some characteristics of the MDFs and discuss them in the context of real rainfall–runoff phenomena observed at the outlet of the small experimental basin that contained the visually observed slope. The following results were obtained. (1) It is roughly estimated that the total amount of sediment discharged by the MDFs was not quantitatively negligible in comparison with the total sediment discharge from the entire experimental basin. (2) The MDFs occurred only during the rising limb of the hydrograph, which lasted 6 min. The visual observation also provided information on triggering conditions. Compared with the precipitation data, it was found that a rainfall intensity of 1 mm min −1 triggered MDFs and an antecedent cumulative rainfall of 10.4 mm was also enough to trigger an MDF. This is consistent with a previous study in Draix. (3) Although the Darcy–Weisbach friction factor and Manning's n of the MDFs observed differ considerably, they are consistent with results in the literature reporting erosion phenomena on very steep slopes up to 36°. (4) Based on this observation and a review of the literature, on very steep and highly erodible slopes, MDFs or similar phenomena might play an important role in erosion and transport processes. It is important to consider this possibility when examining erosion models for catchments composed of steep and erodible slopes.

Water balance comparison of two small experimental basins with different vegetation cover

In a river, the flow directly affects the physical and chemical properties of its water, with further consequences for aquatic biota. Land use practices and vegetation cover play a significant role in the water cycle. The wide-spread perception of forest cover, in terms of hydrology is that forests may reduce water runoff: although in rare instances the contrary has been reported. Water runoff varies seasonally and depends on the forest tree species. By no means can it be considered constant over large expanses of area or for various rainfall patterns. In this paper, the results of a long-term hydrological survey conducted in two experimental microbasins (operated by the Institute of Hydrology SAS, IH SAS) with different land use practices are presented. The Rybarik microbasin (0.119 km 2 ) is dominated by row crop production. The basin was 70% cultivated by the state farm and 30% by a private farm. The Lesný microbasin (0.086 km 2 ) is covered by a deciduous hornbeam regrowth forest (Carpinus betulus). The analysis revealed that the difference in the runoff from the forest and the agricultural land increases with increasing precipitation; however, at some point (extreme precipitations with low probability) the runoff from these basins is nearly equal.

Time‐lapse video observation of erosion processes on the Black Marls badlands in the Southern Alps, France

AbstractIn order to clarify the erosion processes on a marly bare slope in the Southern Alps, the erosion processes in a steep and erodible slope composed of the Black Marls Formation were observed by a time‐lapse video camera. The observations revealed that miniature debris flows (MDFs) occurred at the time of the rainfall‐runoff event in which the most severe erosion took place in the whole observation period of 3 months. Analysis of the camera images showed some characteristics of the MDFs, and these are discussed in the context of real rainfall‐runoff phenomena observed at the outlet of a small experimental basin including the visually observed slope. The following results were obtained. (1) A rough estimation of the total amount of sediment discharge by the MDFs showed that it was not negligible quantitatively. (2) The MDFs occurred only during the rising limb of the hydrograph during 6 minutes. (3) Based on this observation and a review of the literature, in a very steep and highly erodible slope, MDFs or similar phenomena might play an important role in the erosion and transport processes. Copyright © 2008 John Wiley and Sons, Ltd.

Changes in concentration–discharge regression parameters due to coal mining and reclamation activities / Changements dans les paramètres de régression entre concentration et débit, causés par l’exploitation minière de charbon et des activités de reconversion

Assessment of the impacts of mining and reclamation, and design of management practices to reduce chemical loads in stream channels, require knowledge of changing hydrological conditions and of changing sources and rates of release of chemicals into stream waters. One simple method for evaluating these impacts is to combine flow duration curves with regression relations between surface-water chemical concentrations (C) and instantaneous discharge (Q). However, little is known regarding the drainage basin-scale effects of mining and reclaiming drainage basins on regression relations. These effects were assessed on three small experimental drainage basins in Ohio subjected to surface mining for coal. Comparisons were made between regression parameter changes for natural/undisturbed conditions, land disturbances caused by mining and reclamation, incomplete reclamation, and the final condition of the reclaimed drainage basins. Regression analysis used a total of 5047 laboratory analyses of 36 constituents. Of 429 regressions, 153 (36%) were statistically significant. Knowledge of changes in regression parameters is important because regressions supply information on the rate of release and supply of chemical constituents in mined and reclaimed drainage basins. Duration curves of concentration and loads can be constructed using these regressions with flow–duration curves to give estimates of the percentage of time that concentrations and loads are exceeded during different phases of disturbance. This study assessed the changes in regression relations due to mining coal seams and reclamation activities for 36 chemical constituents, two mining methods, three reclamation practices and three distinct geologic settings.

Hydrologic processes and peak discharge response to forest removal, regrowth, and roads in 10 small experimental basins, Western Cascades, Oregon

The magnitude, seasonality, and duration of peak discharge responses to forest removal and regrowth and roads in 10 pairs of experimental basins in the western Cascade Range of Oregon are consistent with fundamental water balance and routing concepts in hydrology. Hypothesized effects of forestry treatments on evapotranspiration, cloud water interception, snowpack dynamics, and subsurface flow interception vary predictably by season, geographic setting, amount of forest canopy removal, stage of canopy regrowth, and arrangement of roads in the basin. Posttreatment responses of selected subpopulations of matched peak discharge events were examined over 10‐ to 34‐year posttreatment periods in treated‐control basin pairs in a range of geographic settings. Changes in evapotranspiration associated with forest canopy removal and regrowth apparently accounted for significant increases (31–116%) in peak discharges during the first postharvest decade in 8 of 10 treated basins, but the events that were affected were small (<0.22‐ or 0.28‐year return periods) and occurred in the fall (September–November), when soils are in moisture deficit, rather than in spring (March–May), when soils are in moisture surplus. For a given amount of forest canopy removal, initial increases in small, fall events were greater in drier basins than wetter basins, and increases tended to disappear as forest canopies regrew. Changes in cloud water interception apparently offset changes in evapotranspiration in two partially cut basins. Changes in snowpack dynamics apparently accounted for significant increases (25–31%) in winter rain‐on‐snow events, but other types of winter events did not change, in four of five basins at the H. J. Andrews Experimental Forest. Changes in subsurface flow interception apparently accounted for significant increases (13–36%) in large (>1‐year return period) events in seven of eight basins with roads, and, controlling for geographic location, the magnitude of increases was related to the density of midslope roads.

Validation of a distributed hydrological model against spatial observations

In connection with climate change studies a new hydrologic field has evolved — regional hydrological modelling or hydrologic macro modelling, which implies repeated application of a model everywhere within a region using a global set of parameters. The application of a physically based distributed hydrological model ECOMAG to river basins within the NOPEX southern region with this purpose in mind is presented.The model considers the main processes of the land surface hydrological cycle: infiltration, evapotranspiration, heat and water regime of the soil, snowmelt, formation of surface, subsurface and river runoff and groundwater. The spatial integration of small and meso-scale non-homogeneity of the land surface is a central issue both for the definition of fundamental units of the model structure and for determination of representative values for model validation. ECOMAG is based on a uniform hydrological (or landscape) unit representation of the river basin, which reflects topography, soil, vegetation and land use. As a first step the model was calibrated using standard meteorological and hydrological data for 7 years from regular observation networks for three basins. An additional adjustment of the soil parameters was performed using soil moisture and groundwater level data from five small experimental basins. This step was followed by validation of the model against runoff for 14 years from six other drainage basins, and synoptic runoff and evapotranspiration measurements performed during two concentrated field efforts (CFEs) of the NOPEX project in 1994 and 1995. The results are promising and indicate directions for further research.

Modelling the subsurface flow component in the runoff recession phase by means of a linear and non-linear reservoir models

The paper deals with the time variability of the subsurface water storage depletion. The analysis was carried out in a small experimental basin in the Jizera Mountains, Czech Republic. The research focused on the hydro graph falling limbs - recession curves - which were selected from daily runoff series using various selection criteria. These criteria include a requirement that a curve should represent subsurface flow which is not increased by surface runoff. The selected measured recession curves are modelled by means of the exponential and hyperbolical law of depletion. The time variability of the recession curves is quantified by the variability of the modelled recession parameters. 22 variables representing antecedent climate and runoff conditions as well as the conditions during the recession period were defined for the examination of possible causing factors of the recession curve time variability. The correlation analysis and the multivariate statistical methods were applied.

Hydrology of Montane Forests in the Sierra de San Javier, Tucuman, Argentina

In Tucuman Province of Argentina, the subtropical moist montane forests, known as Yungas, reach their southern- most limit, occurring between 400 and 2,800 m. The study area is located on the eastern slopes of the Sierra de San Javier where the forest is strongly affected by human pressure. Eighty percent of the annual rainfall in Tucuman falls largely during thunder- storms between October and March. Three recording rain gauges and two fog catchers were installed at 730, 950, and 1,350 m, re- spectively, to study the effect of altitude on the intensity, duration, distribution, and influence of horizontal precipitation. A stream-gauging station has been constructed to measure discharge, floods, and bed load in a small experimental basin in the basal forest. To measure the amount of surface runoff and soil erosion in the basal forest and piedmont area three experimental test plots were installed. The results confirm that deforestation has notably increased hydrological and erosion risk in summer, but also has led to a reduction of water volumes in winter. It was confirmed that the Tucuman montane forests are actual subtropical mon- tane cloud forests. The additional moisture obtained from passing low clouds during the long dry winter season is important and has not yet been considered in the hydrological budget.

Modeling of Nitrogen Cycle and Nitrate Transfer in Regional Hydrogeologic Systems

AbstractA model of the nitrogen cycle and nitrate leaching in soil, called MORELN, was developed to calculate the nitrate flux percolating from soils into aquifers. It uses a “coupled model,” which simulates both surface and subsurface flows. A third model, NEWSAM, is linked to the above models to simulate nitrate migration in an aquifer system. This methodology gives a quantitative global description of nitrate transfer, taking into account both leaching in soils and migration in aquifers. Three examples of application tested this methodology (especially the nitrate leaching code, MORELN) at different scales and with different emphases: (1) in a soil plot of several square meters; (2) in a small experimental basin of several square kilometers; and (3) in a regional hydrogeologic system of several hundred square kilometers. Satisfactory results were obtained for the simulation of nitrate leaching at the small scale. Major differences between the measured and simulated nitrate concentrations were observed in a regional aquifer, where the measured concentration does not spatially correlate and the larger spatial variability of the input data were averaged in the model.

Sediment Yield Observed in a Small Experimental Basin and its Simulation by Runoff-Erosion Modeling

Sediment yield from a small test field with the area of 5200m2in a typically semi-arid region of the north-east of Brazil has been observed for several rainfall events in 1987 and 1988. And the sediment yield is proved to increase remarkably when the total rainfall depth in a continuous rainfall event exceeds 10mm. Sediment yield is directly connected with runoff discharge and is about 5% of the total runoff, and it is well estimated with a runoff-erosion process modeling for rainfall events of the total depth more than 10mm.

Multidimensional Rainfall Parameter Estimation from Sparse Network

The multidimensional precipitation model proposed by Waymire et al. provides realistic representations of the rainfall process. The model, however, in its most simplified form requires the numerical evaluation of nine parameters. Islam et al. developed a parameter estimation procedure and they applied the methodology to a small experimental basin with a dense network of rain gauges. In this paper the same estimation procedure is attempted over a larger area where only a sparse rain‐gauge network is available. Parameter estimates are determined for cyclonic‐midlatitude and convective storms, which are characteristic of the winter and summer rain seasons over the test basin. Using the seasonal storm parameter estimates, multidimensional model storms are generated over the Brazos Valley in Texas, and the storms are assessed qualitatively.

Modélisation du transfert desnitrates dans un système hydrologique

This paper presents a methodology for modeling the transfer, and particularly the leaching of nitrates in a hydrological system such as regional basin. A model of production and leaching of nitrates, called MORELN, was built in order to calculate the nitrates flux percolating from soil into groundwater. It uses the Coupled Model, which simulates integrally the surface and groundwater flows, as the water transfer model. A third model, NEWSAM was employed for modeling the nitrates migration in the aquifer system. The jointed use of these three models gives a global description of the nitrates transfer taking into account both the nitrates production in soils and their displacement in aquifers. Three examples of application allowed us to test this methodology, and especially the MORELN model, on three different scales: in a lysimeter of several m 2 , in a small experimental basin of several km 2 and finally in a regional hydrological system of sevral hundreds km 2

Runoff characteristic and runoff analysis in the Muroran small experimental basin

It is important to clarify the mechanism of runoff process. The authors placed a small experimental basin in the Muroran district and measured rainfall, discharge, ground-water level, capacity of infiltration and water quality. In this paper, we reported the runoff characteristics of small watershed, which were obtained from the hydrological terms.

Modelling of hydrologic processes in a small urbanized hillslope basin with comments on the effects of urbanization

Abstract A small urbanized experimental basin with a catchment area of 2.8 ha, in the Tama hills in the western suburbs of Tokyo, Japan, called the Nagayama Basin, has been studied. The site has rain-recording and streamflow gaugings as well as soil-moisture measuring instruments and groundwater observation wells. Initially, based upon the observed data, the partial hydrologic processes, such as direct runoff, rainfall-loss, groundwater runoff, groundwater recharge, and evapotranspiration, are respectively analyzed. Subsequently, daily and hourly hydrological watershed models are constructed by synthesizing the results, and their applicability is examined. Finally, these models are compared with the models obtained for a natural experimental basin with a catchment area of 4.4 ha, located on the same Tama hills, and the effects of urbanization on hydrologic processes are commented on.

Groundwater-runoff Analysis in Small Experimental Basin

Groundwater-runoff Analysis in Small Experimental Basin

Modelling of hydrologic processes in a small natural hillslope basin, based on the synthesis of partial hydrological relationships

The authors have equipped a natural small experimental basin, with a catchment area of 4.4 ha, in the Tama Hills in the western suburbs of Tokyo, Japan. It has not only precipitation and streamflow gauging but also soil moisture measuring instruments and groundwater observation wells. At first, based upon the observed data, the partial hydrologic processes such as direct runoff, rainfall-loss, groundwater runoff, groundwater recharge, and evapotranspiration are analyzed. Then a daily hydrological model and an hourly hydrological model are constructed by synthesizing the results of the above analysis, and their applicability is examined.

On Hydrological Cycle in a Small Experimental Basin Equipped in a Hilly Land

On Hydrological Cycle in a Small Experimental Basin Equipped in a Hilly Land

Effet du pourcentage et de la distribution des surfaces boisées sur les crues de fonte de neige

Following a review of the influence of deforestation on basin runoff, it is shown how a mathematical model could be used advantageously to simulate the effect of a variation in forest cover on snowmelt runoff and provide important data for basin management. Whereas most of the previous investigations were dealing with small experimental basins, simulations with the CEQUEAU square-grid system model on a > 3000 km 2 basin confirm clearly the possibility to modify the snowmelt synchronization between different parts of a basin by changing the distribution and/or percentage of its forest cover. For instance, in the given example, if the forest cover had been distributed uniformly so as to occupy 50% of the total area of the basin, the maximum runoff would have been reduced by approximately one third, whereas a complete deforestation over 670 m would have led to a larger maximum runoff.