Large Scale Basins With Small to Negligible Slopes

2000 ◽  
Vol 31 (1) ◽  
pp. 27-40 ◽  
Author(s):  
Luis Silveira
Keyword(s):  
Soil Moisture ◽  
Large Scale ◽  
Hydrological Model ◽  
Transport Processes ◽  
Moisture Condition ◽  
Soil Moisture Condition ◽  
Soil Moisture Storage ◽  
High Soil Moisture ◽  
Rio Negro ◽  
Moisture Storage

Large basins with small to negligible slopes are seldom considered in the hydrological literature. An example of such basins is the Río Negro catchment in Uruguay. The first of this two-paper series showed the following special features: a) the existence of strongly developed horizontal layers and an essentially impervious B-horizon, b) significantly high soil moisture storage in terms of normally expected rainfall during a storm and c) the importance of vertical water transport processes to establish the soil moisture condition prior to a storm and its role concerning basin runoff response. These observations and hypotheses were taken into account by the lumped conceptual hydrological model called Hidro-Urfing through the percolation function and the basin runoff response function. This second paper shows its application to the Laguna I basin, a sub-basin of the Río Negro catchment with a surface area of 13,945 km2, and its ability to model the major storm hydrographs without any subdivision into smaller sub-basins. Modelling of low flows requires disaggregation of spatial-scale issues. A hydrological model of the entire Río Negro catchment did not previously exist.

scholarly journals Large Scale Basins With Small to Negligible Slopes

2000 ◽  
Vol 31 (1) ◽  
pp. 15-26 ◽  
Author(s):  
Luis Silveira
Keyword(s):  
Soil Moisture ◽  
Large Scale ◽  
Subsurface Flow ◽  
Transport Processes ◽  
Runoff Generation ◽  
Soil Moisture Storage ◽  
Accumulated Rainfall ◽  
Physical Features ◽  
Rio Negro Basin ◽  
Surface And Subsurface Flow

In the first of this two-paper series, the main mechanisms for generation of runoff from rainfall in large basins with small to negligible slopes are analyzed using available data from the Río Negro basin in Uruguay. Topography and soils were examined in order to identify physical features that may influence the flow patterns. Soil moisture storage in space and soil moisture variability in time were also evaluated to relate rainfall and runoff generation. The study revealed the existence of strongly developed horizontal layers. Soil moisture depends essentially on vertical water transport processes due to the low morphological energy of the terrain. Surface and subsurface flow occurs during the season of low evapotranspiration where soils become progressively wet. Extreme storms in terms of accumulated rainfall are required to produce surface and subsurface flow during the season of high evapotranspiration. In the following paper, these observations and hypotheses are used to model a large basin with small to negligible slopes.

scholarly journals Scale issues in soil moisture modelling: problems and prospects

1996 ◽  
Vol 20 (3) ◽  
pp. 273-291 ◽  
Author(s):  
Rezaul Mahmood
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Surface Characterization ◽  
Large Scale ◽  
Small Scale ◽  
Soil Moisture Storage ◽  
Surface Atmosphere ◽  
Physically Based ◽  
Physically Based Models ◽  
Moisture Storage

Soil moisture storage is an important component of the hydrological cycle and plays a key role in land-surface-atmosphere interaction. The soil-moisture storage equation in this study considers precipitation as an input and soil moisture as a residual term for runoff and evapotranspiration. A number of models have been developed to estimate soil moisture storage and the components of the soil-moisture storage equation. A detailed discussion of the impli cation of the scale of application of these models reports that it is not possible to extrapolate processes and their estimates from the small to the large scale. It is also noted that physically based models for small-scale applications are sufficiently detailed to reproduce land-surface- atmosphere interactions. On the other hand, models for large-scale applications oversimplify the processes. Recently developed physically based models for large-scale applications can only be applied to limited uses because of data restrictions and the problems associated with land surface characterization. It is reported that remote sensing can play an important role in over coming the problems related to the unavailability of data and the land surface characterization of large-scale applications of these physically based models when estimating soil moisture storage.

scholarly journals An Analytical Hydrological Model for the Study of Scaling Issues in Land Surface Modeling

2006 ◽  
Vol 10 (20) ◽  
pp. 1-24 ◽  
Author(s):  
Diandong Ren ◽  
Ann Henderson-Sellers
Keyword(s):  
Soil Moisture ◽  
Steady State ◽  
Analytical Model ◽  
Hydrological Model ◽  
Clay Soil ◽  
Initial Conditions ◽  
Moisture Condition ◽  
Soil Moisture Condition ◽  
Initial Soil Moisture ◽  
Initial Soil

Abstract Besides the atmospheric forcing such as solar radiation input and precipitation, the heterogeneity of the surface cover also plays an important role, especially in the distribution characteristics of the latent heat flux (LE). In this study, scaling issues are discussed based on an analytical hydrological model that describes the transpiration and diffusion processes of soil water. The solution of this analytical model is composed of a transient part that depends primarily on initial conditions and a steady part that depends on the boundary conditions. To know how sensitive the different averaging approaches are to the initial conditions, three initial profiles are chosen that cover the prevailing soil moisture regimes. After analyzing its solution, the study shows that 1) upon reaching the steady state, directly taking an average of soil properties will cause systematic overestimation in the calculation of area-averaged LE. For an initially very dry condition, averaging of a sandy soil and a clay soil can cause a percentage error as large as 40%. 2) For vegetation growing on sandy soils, a direct averaging of the transpiration rate results in persistent overestimation of LE. For vegetation growing on clay soil, however, even after reaching the steady state, averaging of two water extraction weights can be either an overestimation or an underestimation, depending on which two vegetation types are involved. 3) During the interim stage of drying down, averaging of the soil/vegetation properties can lead to either an overestimation or an underestimation, depending on the evolving stage of the soil moisture profile. 4) The initial soil moisture condition matters during the transient stage of drying down. Different initial soil moisture conditions yield different scenarios of underestimation and overestimation patterns and a differing severity of errors. The simplicity of the analytical model and the heuristic initial soil profiles make the generalization easier than using sophisticated numerical models and make the causality mechanism clearer for physical interpretations.

scholarly journals Operational aspects of asynchronous filtering for flood forecasting

2015 ◽  
Vol 19 (6) ◽  
pp. 2911-2924 ◽  
Author(s):  
O. Rakovec ◽  
A. H. Weerts ◽  
J. Sumihar ◽  
R. Uijlenhoet
Keyword(s):  
Soil Moisture ◽  
Ensemble Kalman Filter ◽  
Hydrological Model ◽  
Soil Moisture Storage ◽  
Operational Forecasting ◽  
Model Update ◽  
Moisture Storage ◽  
Forward Integration ◽  
Grid Based ◽  
Operational Aspects

Abstract. This study investigates the suitability of the asynchronous ensemble Kalman filter (AEnKF) and a partitioned updating scheme for hydrological forecasting. The AEnKF requires forward integration of the model for the analysis and enables assimilation of current and past observations simultaneously at a single analysis step. The results of discharge assimilation into a grid-based hydrological model (using a soil moisture error model) for the Upper Ourthe catchment in the Belgian Ardennes show that including past predictions and observations in the data assimilation method improves the model forecasts. Additionally, we show that elimination of the strongly non-linear relation between the soil moisture storage and assimilated discharge observations from the model update becomes beneficial for improved operational forecasting, which is evaluated using several validation measures.

Impact of climate change on soil moisture condition in Nova Scotia

2012 ◽  
Author(s):  
Raheleh Malekian ◽  
Robert Gordon ◽  
Ali Madani ASABE Member ◽  
Seyyed Ebrahim Hashemi
Keyword(s):  
Climate Change ◽  
Soil Moisture ◽  
Nova Scotia ◽  
Moisture Condition ◽  
Soil Moisture Condition ◽  
Impact Of Climate Change

scholarly journals Effect of soil moisture condition on the conversion rate of oxamyl.

1979 ◽  
Vol 27 (3) ◽  
pp. 191-198
Author(s):  
J.H. Smelt ◽  
A. Dekker ◽  
M. Leistra
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Conversion Rate ◽  
Soil Moisture Content ◽  
Loamy Sand ◽  
Clay Loam ◽  
Moisture Condition ◽  
Soil Moisture Condition ◽  
Incubation Experiments ◽  
Wilting Point

The decomposition of oxamyl in four soils under moist conditions was measured in incubation experiments at 15 deg C. Half-lives of oxamyl in soils with moisture tensions of approx. -9.8 X 103 Pa were 13 days in a clay loam, 14 days in a loamy sand, 34 days in a peaty sand and 39 days in a humic loamy sand. The rate of oxamyl decomposition in the clay loam decreased with decreasing soil moisture content down to values for below wilting point. Oxamyl decomposition in the humic loamy sand decreased with decreasing soil moisture content, but increased sharply in the very dry range. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals Soil moisture obtained through remote sensing to assess drought events

2020 ◽  
Vol 24 (9) ◽  
pp. 575-580 ◽  
Author(s):  
Tiago de M. Inocêncio ◽  
Alfredo Ribeiro Neto ◽  
Alzira G. S. S. Souza
Keyword(s):  
Climate Change ◽  
Soil Moisture ◽  
Condition Index ◽  
Semiarid Region ◽  
Moisture Index ◽  
Moisture Condition ◽  
Soil Moisture Condition ◽  
Northeast Region ◽  
Promising Tool ◽  
Soil Moisture Index

ABSTRACT The sequence of drought events in the Northeast of Brazil in recent decades raises attention to the importance of studying this phenomenon. The objective of this study was to evaluate the duration and severity of drought events from 1988 to 2018 in hydrographic basins of the state of Pernambuco, Brazil, using two drought indexes: Standardized Soil Moisture Index and Soil Moisture Condition Index, calculated based on data of the Soil Moisture Project of the European Space Agency’s Climate Change Initiative. The duration of the droughts was determined considering the months between their beginning and end, and their severity was based on the area formed in the graph between the curve of the index and the x-axis. The soil moisture database showed to be a promising tool for the analysis and monitoring of drought events in the Northeast region of Brazil, mainly for analysis and monitoring of drought events. The indexes allowed the evaluation of the drought phenomenon over the 30-year period, showing increases from 2012, which were more pronounced in the Semiarid region. The hydrographic basins responded differently to a same event, depending on the climate characteristics of the region in which they are located. Consecutive years with rainfall below the historical mean increased the magnitude of the droughts, as found for the 2012-2017 period, in which the indexes presented delays to return to more favorable values, showing the effect that one drought year has on the following year.

Dark Island heath (Ninety-mile Plain, South Australia). V. The water relationships in heath vegetation and pastures on the Makin sand

1957 ◽  
Vol 5 (2) ◽  
pp. 151 ◽  
Author(s):  
RL Specht
Keyword(s):  
Soil Moisture ◽  
Balance Sheet ◽  
South Australia ◽  
Field Capacity ◽  
Severe Drought ◽  
Soil Moisture Storage ◽  
Drought Conditions ◽  
Moisture Storage ◽  
Medicago Sativa L ◽  
Soil Moisture Status

Heath vegetation shows a major flush of growth during the mediterraneantype summer season, a time when calculations of the soil moisture storage by the techniques of Thornthwaite (1948) or Prescott, Collins, and Shirpurkar (1952) indicate that severe drought conditions should oocur. Monthly observations on the moisture status of the Makin sand under heath vegetation and, for comparison, under various pastures are therefore recorded. The problems of obtaining an accurate water balance-sheet for such a heterogeneous vegetation as the heath are discussed. Difficulties in the use of the various techniques for measuring soil moisture in sand, which has a low pF of 1.85 at field capacity, are enumerated. The following relationships were found between the evapotranspiration index (Itr = Etr / Ew0.75) and the available water (W). These data were calculated for 6 ft of sand. (i) Heath vegetation (10–14 years old) log (2.4–Itr) = 0.420–0.0383 W (ii) Heath vegetation (burnt) log (2.4–Itr) = 0.461–0.0380 W (iii) Oenothera odorata Jacq. pasture log (2.4–Itr) = 0.395–0.0269 W (iv) Medicago sativa L. pasture log (2.4–Itr) = 0.390–0.0270 W (v) Ehrharta calycina Sm. pasture log (2.4–Itr) = 0.400–0.0339 W From these equations the mean monthly quantities of rainfall which may be stored in 6 ft of sand under the various treatments described were calculated. Drought conditions are shown to occur in December and January, but are relieved in the later months of summer. Even if the stored moisture below 8 ft is considered, the soil moisture status would be expected to be just sufficient to maintain the vegetation in a "dormant" state, and yet the major growth of the heath vegetation occurs at this time. The calculated mean annual values of Itr range from 0.53 to 0.60 for these perennial communities. Close approximations to the actual soil moisture status can be obtained by substituting these values for K in Prescott's formula for potential evaporation, i.e. Etr = K x Ew0.75. Supplementary data on transpiration, growth, and the root systems of the pastures are also included.

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