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Content:
Vol.
7, No. 2 Fall 2007
Vol.
7, No. 1 Spring 2007
Vol.
6, No. 2 Fall 2006
Vol.
6, No. 1 Spring 2006
Vol. 5, No. 2 Fall 2005
Vol.
5, No. 1 Spring 2005
Vol.
4, No. 2 Fall 2004
Vol.
4, No. 1 Spring 2004
Vol.
3, No. 2 Fall 2003
Vol.
3,
No. 1 Spring
2003
Vol. 2,
No. 2 Fall 2002
Vol. 2,
No. 1 Spring 2002
Vol. 1, No. 1 Fall 2001
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Classification of Spatio
-Temporal Pattern of Rainfall in Iran Using A Hierarchical and
Divisive Cluster Analysis
Saeed Soltani
and Reza Modarres
Abstract: The identification of spatial rainfall pattern is an
essential task for hydrologists, climatologists as well as regional
and local planners and managers. This is due to the variability of
both the temporal spatial distribution of rainfall. In this study, a
hierarchical and divisive cluster analysis was used to categorize
these patterns of rainfall in Iran. According to results obtained,
there are eight main spatial groups of annual rainfall over Iran.
These groups can be classified into 3 main seasonal rainfall regimes
namely, winter, winter-spring and fall regimes. The results also
show that the elevation and sea neighborhood affect rainfall pattern
of Iran. Moreover, a comparison between the Ward and average methods
of hierarchical cluster analysis indicates that the Ward method
performs the spatial pattern better.Key Words: Rainfall pattern, Cluster Analysis, Ward Method,
Iran
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Mapping of
contamination plumes at municipal solid waste disposal sites using
geoelectric imaging technique: Case studies in Malaysia Abdul Rahim Samsudin, Bahaa-eldin
Elwali A.Rahim,Wan Zuhairi Wan Yaacob & Umar Hamzah
Abstract:
Municipal solid waste disposal sites can be sources of groundwater
contamination and the contamination problems are more likely to
occur in humid areas, where the moisture available exceeds the
ability of the waste pile absorb water. In tropical country like
Malaysia which is characterized by high rainfall, the subsurface
contamination problems are expected to occur. Seriousness of the
pollution problem is still unknown and specific detailed study is
generally needed. Two dimensional geoelectrical imaging has
frequently been used in the subsurface pollution studies. The method
maps the distribution of resistivity of subsurface materials. The
resistivity image provides general information on subsurface
stratification of buried waste and contaminated soil, as well
the depth to the bedrock below the lines of traverse. Underground
soil or water that has been contaminated by leachate usually has a
significantly lower resistivity value. This paper discusses the
results of the 2-D resistivity imaging which were conducted to
identify and delineate the extent of contaminated soil and leachate
plumes, as well as to assess the capability of the 2-D resistivity
imaging as a pre-characterization tool for tracing the properties of
disposed waste and its severity underneath a capped landfill sites.
The imaging method was used in this study to map the contaminated
subsurface soil and ground water at three municipal solid waste
disposal sites namely Ampar Tenang (AT) open-tipping site, Bukit
Kemuning (BK) capped landfill, and Taiping landfill (TL) where a
total of twenty two 2-D resistivity lines were surveyed. The surveys
were conducted using ABEM SAS1000 resistivity meter and LUND
Automatic imaging system and the measured resistivity profiles were
interpreted using 2-D resistivity inversion programme (RES2DINV).
Generally the results of the measured resistivity values obtained
from the three sites define the contaminated leachate plumes as
electrically conductive anomalies of relatively low resistivity
value less than 10 ohm-m.Key words :
2-D Resistivity imaging, solid waste,
disposal sites, and leachate plume.
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Estimating Limiting Nutrient
Loadings in an Interacting Surface and Ground Water Basin
Ahmed
Said
Abstract: Watershed management requires the
determination of both point and non-point sources of pollution
within a watershed. The primary non-point source pollutants in a
typical watershed are nutrients (mainly nitrogen and phosphorus),
sediment, and pesticides. In the Snake River Basin, in Idaho,
nutrients from non-point sources (primarily agricultural) are
delivered to streams via storm water and irrigation runoff. However,
the objectives of this study were to estimate the phosphorus loading
from different sources in the Snake River Basin due to storm water
events, to calculate the total nitrogen/phosphorus (TN/TP) ratios
for land uses, and to compare and a precipitation runoff model and
statistical regression with the measurements. The study used the
Long-Term Hydrologic Impact Assessment (L-THIA) model to perform the
analysis and to estimate the loss and gain in phosphorus loading.
The gain was due to ground water discharge and point sources from
industrial and commercial trout farms. The loss was attributed to
phosphorus absorbance, existence of riparian vegetation, ground
water discharge, or dilution from spring inflows. The results showed
that phosphorus is the limiting nutrient. The L-THIA model gave more
accurate results than the simple statistical regression.
Key Words: L-THIA model, water quality, sediment, Snake River
Basin, Idaho
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Development of a Multivariate
Regression Model for Soil Nitrate Nitrogen Content Prediction
Xixi Wang, Assefa M. Melesse, and
Wanhong Yang
Abstract: Although soil
nitrate nitrogen (N) is a nutrient source for crop, it could be a
potential nonpoint pollution source to the environment when its
content remains high with an inappropriate management. Soil nitrate
N content is affected by various factors, such as cultivation
practices, N fertilizer application rate, soil properties, and
climatic conditions. Understanding the effects of these factors on
soil nitrate N content is necessary for nitrogen management and
nonpoint source pollution control. Taking the data measured from
1996 to 1998 in a 25 ha row crop field located in Central Iowa, this
paper intended to study the interwoven effects of these factors on
soil nitrate N content using multivariate statistical analysis
techniques of sample mean plots, a multivariate analysis of variance
(MANOVA) model, and a multivariate linear regression model. The
inferences made by the sample mean plots and MANOVA model indicate
that the effects of these factors are additive, i.e., their main or
direct effects are statistically significant but the interaction
effects between and among them are insignificant at a 5%
significance level. Incorporating these additive effects, a
multivariate linear regression model was fitted to the dataset. The
residual plots show that the dataset follows an approximate
bivariate normal distribution, which is assumed by the MANOVA and
multivariate linear regression models. The validation using the
field data collected in 1999 indicated that the model explained more
than 93% variations exhibited by the measured sublayed-averaged data
on soil nitrate N content and soil moisture. However, this model is
unable to account for the within-sublayer variations.Key words: linear regression; multivariate statistics; nitrogen; NPS; soil
moisture; spatial analysis; visualization.
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Abstract: An
approach to estimate the curve number (CN) at each pixel unit of a
satellite imagery, which is a key parameter in the widely used Soil
Conservation Service Curve Number (SCSCN) hydrologic model, is
proposed. Instead of mapping land use and its temporal dynamics from
satellite imageries, this approach linearly unmixes the
multi-spectral radiances into three fractional layers which
primarily control the degree of saturation within a watershed
occurring due to a 25 cm-depth storm event, i.e., physically
interpreted as the CN. The fraction layers used are water, sand and
pure vegetation. In order to obtain a relationship between the
fractional statistics and CN, a multi-correlationship analysis of
known combinations of land use, hydrologic condition and hydrologic
soil group is carried out in an agricultural watershed. The obtained
relationship is applied onto the fractional layers to compute the
spatial distribution of CN. The performance of the SCS-CN model with
the spatial CN is found to be 14% more accurate than that of the
model results with only land use information from satellite
imageries. The spatial difference of two CN layers in which the one
represents the condition of the watershed before soil and water
conservation measures was taken up and the other for the post
conservation period indicates change in the hydrologic response of
the watershed spatially.
Key words: Curve Number;
Satellite Imagery; Watershed modeling; GIS.
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Estimation of Aquifer
Transmissivity using Kriging, Artificial Neural Network, and
Neuro-Fuzzy models
M. Kholghi and
S.M. Hosseini
Abstract: In interpolation of groundwater
properties such as transmissivity, due to the unknown distributed
values of the variables and heterogenity, the best and the unbiased
aspects are frequently difficult to obtain. Therefore, applying a
modern technique is necessary to obtain a real estimation of
transmissivity. To gain the transmissivity values as an input data
in groundwater modelling, the ordinary log kriging method has been
used. In this study, the efficiency of the Adaptive Network based
Fuzzy Inference System (ANFIS), artificial neural networks and
ordinary kriging are investigated for interpolation of
transmissivity in an unconfined aquifer. The results indicate that
ANFIS model is more efficient to estimate the transmissivity in
comparison with the ANN and kriging models. With these
results, we can propose ANFIS model to interpolate the
transmissivity values in groundwater modelling processes.
Keywords: Transmissivity ,
Kriging, Artificial Neural Network, ANFIS.
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Predicting runoff and
phosphorus loads from variable source areas A terrain-based spatial
modelling approach
P.J. Davies, J.W. Cox, N.K. Fleming,
W.J. Dougherty, D.M. Nash and J.L. Hutson
Abstract:Research has been conducted at Flaxley Agricultural Centre in
South Australia to predict phosphorus loss in surface runoff from
dairy pastures. Part of the research investigated if the topography
based, spatially distributed hydrological model - TOPMODEL could be
adapted to successfully predict phosphorus loads off dryland and
irrigated catchments, where variable source area hydrology is
considered a dominant process. This was carried out by integrating
one season of field measured runoff and P load data with rainfall
and evapotranspiration data. The methodology uses TOPMODEL to
simulate runoff volume and spatial extent of saturated areas, using
a topographic index - ln(As/tanB) to distribute variable source
areas across catchments, within a loose coupled GIS framework. Using
the simulations of runoff from the dryland and irrigated catchments,
phosphorus loads in surface runoff were then simulated, using an
empirically established, terrain-based phosphorus load index
relatable to variable source runoff (TOPMODEL-PLI).
TOPMODEL was found to model runoff for dryland and irrigated
catchments with some success, based upon one season of monitoring
data. The dynamics of runoff events were reasonably accurately
predicted. There was a tendency for TOPMODEL to over predict runoff
volumes from catchments with a high average topographic index and
under predict runoff volumes from catchments with a low average
index. Results of modelling P loads using TOPMODEL-PLI for dryland
and irrigated catchments were encouraging but the model tended to
over estimate total P loads volumes off all catchments. A case
assessment of the predicted P loads for one dryland and one
irrigated catchment showed they were well within acceptable error
limits. The modelled P load results may, in part be due to the
accuracy of the load index that was used in TOPMODEL. Two issues are
identified - the interpolation of soil P surfaces and robustness of
the soil P-runoff P relationship used to establish the load index.
TOPMODEL-PLI performance for catchments at FAC is encouraging.
Although the prediction of P load was within acceptable error it may
be improved by further research into the soil P:runoff P
relationship which underpins the phosphorus load index.
Keywords: TOPMODEL,
Hydrological modelling, terrain analysis, surface water, phosphorus
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Erosion Risk Assessment using
an Empirical Model of Pacific South West Inter Agency Committee
Method for Zargeh Watershed, Iran
Ramin
Safamanesh, Wan Nor Azmin
Sulaiman and Mohammad Firuz Ramli
Abstract: Watershed degradation due to soil erosion and sedimentation is one
of the major environmental problems in Iran. In addressing the
issue, a study on the validity of an empirical model of Pacific
South West Inter Agency Committee Method (MPSIAC) to predict annual
average sediment yield to Zargeh watershed was undertaken. The
MPSIAC method incorporates nine environmental factors that
contribute to sediment yield of the watershed namely: surface
geology, soil, climate, runoff, topography, ground cover, land use,
channel and upland erosion. Open-source Geographic Resources
Analysis Support System (GRASS) was used to facilitate the spatial
interpolation of the nine model factors and interpretation of
predicted sediment yield for the entire watershed. Twenty year
sediment yield records from 1980 to 1999 were used to validate the
simulated model results. Simple linear regression analysis between
simulated model results and actual field records indicated that
there was a significant correlation (P < 0.05) with r2
= 0.6124. The results suggested
that the model is suitable for predicting yearly average sediment
yield on a long term basis fo the Iranian watersheds with similar
conditions.
Keywords: MPSIAC,
Erosion, Sediment Yield.
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Estimation of aquifer
hydraulic characteristics from electrical sounding data: the case of
middle Imo River basin aquifers, south- eastern Nigeria
A.C. Ekwe, N.N. Onu and K.M.Onuoha
Abstract:
We have used the concept of Da -
Zarrouk parameters (transverse unit resistance (R) and longitudinal
conductance (C)) in porous media to determine aquifer hydraulic
characteristics within the middle Imo river basin. The
lithostratigraphic units within the study area include: Imo
formation, Bende - Ameki formation, Ogwashi Asaba formation and
Benin formation. The direct current electrical resistivity method
was utilized for the present study. Twenty-four (24) vertical
electrical soundings (VES) using the Schlumberger array was acquired
for the study area. A maximum current electrode spacing (AB) of 1000
meters was used. Eight of the soundings were carried out near
existing boreholes. A combination of curve matching techniques and
computer iterative modelling was used in processing the data.
Results show that the depth to water table varies between 12m
at Ife and 153m at Aba Branch. Interpretative cross - section along
two profiles show that aquifer thicknesses range between 9m and
104m. The diagnostic Kσ = constant value was used to delineate
the different lithostratigraphic units within the study area. We
have also used the established relationship between aquifer
characteristics and geoelectric parameters to estimate hydraulic
conductivity and transmissivity values of all the sounding locations
including areas where boreholes were non - existent. Hydraulic
conductivity varies between 1.24 m/day at Amuzukwu and 26.41 m/day
at Obinze. Transmissivity values also vary between 41m2/day
at Osuachara and 1370 m2/day
at Obinze.
Keywords: Aquifer hydraulic characteristics, Dar - Zarrouk parameters,
Resistivity, Imo River Basin, Nigeria.
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JoSHJournal
of Spatial Hydrology
ISSN: 1530-4736