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1.
The nonlinear Boussinesq equation is used to understand water table fluctuations in various ditch drainage problems. An approximate solution of this equation with a random initial condition and deterministic boundary conditions, recharge rate and aquifer parameters has been developed to predict a transient water table in a ditch-drainage system. The effects of uncertainty in the initial condition on the water table are illustrated with the help of a synthetic example. These results would find applications in ditch-drainage design.Notation
A
/ tanh t
-
a
lower value of the random variable representing the initial water table height at the mid point
-
a+b
Upper value of the random variable representing the initial water table height at the midpoint
-
B
tanh t
-
C
4/
-
h
variable water table height
- h
mean of the variable water table height
-
h
m
variable water table height at the mid point
- h
m
mean of the variable water table height at the mid point
-
K
hydraulic conductivity
-
L
half spacing between the ditches
-
m
0
initial water table height at the mid point
-
N
Uniform rate of recharge
-
S
specific yield
-
t
time of observation
-
x
distance measured from the ditch boundary
-
(4/SL)(NK)1/2
-
(L/4)(N/K)1/2
-
dummy integral variable 相似文献
2.
A unit hydrograph (UH) obtained from past storms can be used to predict a direct runoff hydrograph (DRH) based on the effective rainfall hyetograph (ERH) of a new storm. The objective functions in commonly used linear programming (LP) formulations for obtaining an optimal UH are (1) minimizing the sum of absolute deviations (MSAD) and (2) minimizing the largest absolute deviation (MLAD). This paper proposes two alternative LP formulations for obtaining an optimal UH, namely, (1) minimizing the weighted sum of absolute deviations (MWSAD) and (2) minimizing the range of deviations (MRNG). In this paper the predicted DRHs as well as the regenerated DRHs by using the UHs obtained from different LP formulations were compared using a statistical cross-validation technique. The golden section search method was used to determine the optimal weights for the model of MWSAD. The numerical results show that the UH by MRNG is better than that by MLAD in regenerating and predicting DRHs. It is also found that the model MWSAD with a properly selected weighing function would produce a UH that is better in predicting the DRHs than the commonly used MSAD.Notations
M
number of effective rainfall increments
-
N
number of direct runoff hydrograph ordinates
-
R
number of storms
- MSAD
minimize sum of absolute deviation
- MWSAD
minimize weighted sum of absolute deviation
- MLAD
minimize the largest absolute deviation
- MRNG
minimize the range of deviation
- RMSE
root mean square error
-
P
m
effective rainfall in time interval [(m–1)t,mt]
-
Q
n
direct runoff at discrete timent
-
U
k
unit hydrograph ordinate at discrete timekt
-
W
n
weight assigned to error associated with estimatingQ
n
-
n
+
error associated with over-estimation ofQ
n
-
n
–
error associated with under-estimation ofQ
n
-
max
+
maximum positive error in fitting direct runoff hydrograph
-
max
–
maximum negative error in fitting direct runoff hydrograph
-
max
largest absolute error in fitting obtained direct runoff
-
E
r,1
thelth error criterion measuring the fit between the observed DRHs and the predicted (or reproduced) DRHs for therth storm
-
E
1
averaged value of error criterion overR storms 相似文献
3.
Soil-water distribution in homogeneous soil profiles of Yolo clay loam and Yolo sand (Typic xerorthents) irrigated from a circular source of water, was measured several times after the initiation of irrigation. The effect of trickle discharge rates and soil type on the locations of the wetting front and soil-water distribution was considered. Soil-water tension and hydraulic conductivity, as functions of soil-water content, were also measured. The theories of time-dependent, linearized infiltration from a circular source and a finite-element solution of the two-dimensional transient soil-water equation were compared with the experimental results. In general, for both soils the computer horizontal and vertical advances of the wetting front were closely related to those observed. With both theories, a better prediction of the wetting front position for the clay loam soil than for the sandy soil is shown. The calculated and measured horizontal vertical advances did not agree over long periods of time. With the linearized solution, overestimated and underestimated vertical advances for the clay and sandy soils, respectively, were shown. The finite-element model approximate in a better way the vertical advances than the linearized solution, while an opposite tendency for the horizontal advances indicated, especially in sandy soil.Notation
k
constant (dK/d)
-
K
hydraulic conductivity
-
K
0
saturated hydraulic conductivity
-
J
0,J
1
Bessel functions of the first kind
-
h
soil water tension
-
q
Q/r
0
2
-
Q
discharge rate
-
r
cylindrical coordinate; also horizontal distance in soil surface
-
R
dimensionless quantity forr
-
r
0
constant pond radius
-
R
0
dimensionless quantity forr
0
-
t
time
-
T
dimensionless quantity fort
-
x, y
Cartesian coordinates
-
z
vertical coordinate; also vertical distance along thez axis chosen positively downward
-
Z
dimensionless quantity forz
-
empirical soil characteristic constant
-
dummy variable of integration
-
volumetric soil water content
-
matrix flux potential
-
dimensionless quantity for 相似文献
4.
The MESA-based model, developed in the first paper, for real-time flood forecasting was verified on five watersheds from different regions of the world. The sampling time interval and forecast lead time varied from several minutes to one day. The model was found to be superior to a state-space model for all events where it was difficult to obtain prior information about model parameters. The mathematical form of the model was found to be similar to a bivariate autoregressive (AR) model, and under certain conditions, these two models became equivalent.Notation
A
k
parameter matrix of the bivariate AR model
-
B
backshift operator in time series analysis
-
eT
forecast error (vector) at timet = T
-
t
uncorrelated random series (white noise)
-
F
k
forward extension matrix of the entropy model forkth lag
-
I
identity matrix
-
m
order of the entropy model
-
N
number of observations
-
P
order of the AR model
-
Q
p
peak of the direct runoff hydrograph
-
R
correlation matrix
-
t
p
time to peak of the direct runoff hydrograph
-
1
coefficient of variation
-
2
ratio of absolute error to the mean
-
forecasted runoff
-
x
i
observed runoff
-
mean of the observed runoff
-
X
–1
inverse ofX matrix
-
X*
transpose of theX matrix
Abbreviations AIC
Akaike information criterion
- AR
autoregressive (model)
- AR(p)
autoregressive process of thepth order
- ARIMA
autoregressive integrated moving average (model)
- acf
autocorrelation function
- ccf
cross-correlation function
- FLT
forecast lead time
- MESA
maximum entropy spectral analysis
- MSE
mean square error
- STI
sampling time interval 相似文献
5.
Proper well management requires the determination of characteristic hydraulic parameters of production wells such as well loss coefficient (C) and aquifer loss coefficient (B), which are conventionally determined by the graphical analysis ofstep-drawdowntest data. However, in the present study, the efficacy of a non-conventional optimization technique called Genetic Algorithm (GA), which ensures near-optimal or optimal solutions, is assessedin determining well parameters from step-drawdown test data. Computer programs were developed to optimize the well parametersby GA technique for two cases: (i) optimization of B and C only, and (ii) optimization of B, C and p (exponent) as well as to evaluate the well condition. The reliability and robustness of the developed computer programs were tested usingnine sets of published and unpublished step-drawdown data from varying hydrogeologic conditions. The well parameters obtained by the GA technique were compared with those obtained by the conventional graphical method in terms of root mean square error(RMSE) and visual inspection. It was revealed that the GA technique yielded more reliable well parameters with significantlylow values of RMSE for almost all the datasets, especially in caseof three-variable optimization. The optimal values of the parametersB, C and p for the nine datasets were found to range from 0.382 to 2.292 min m-2, 0.091 to 3.262, and 1.8 to 3.6, respectively. Because of a wide variation of p, the GA techniqueresulted in considerably different but dependable and robust well parameters as well as well specific capacity and well efficiency compared to the graphical method. The condition of three wells was found to be good, one well bad and that of the remaining five wells satisfactory. The performance evaluation of the developed GA code indicated that a proper selection of generation number and population size is essential to ensure efficient optimization. Furthermore,a sensitivity analysis of the obtained optimal parameters demonstrated that the GA technique resulted in a unique set ofthe parameters for all the nine datasets. It is concluded thatthe GA technique is an effective and reliable numerical tool for determining the characteristic hydraulic parameters of production wells. 相似文献
6.
Use of parameter estimation in determining soil hydraulic properties from unsaturated transient flow
This paper proposes a model for determining the parameters given by the closed-form equations of van Genuchten. An objective function is made by the observed data from vertical drainage, and the solutions of optimization show that less computation and more accurate estimates are made as head profiles are taken into account rather than cumulative drainage. Sensitivity analysis of the error vector to parameters interprets this reason. The convergence and stability of solutions are evaluated with different magnitudes of measured errors in the head, and the results show good estimates will be obtained if a sufficient pressure head at the soil bottom is applied. A variable
k
is introduced to avoid the estimations of and n being affected by the uncertainties of Ks and
s
. 相似文献
7.
Forecast model of water consumption for Naples 总被引:1,自引:1,他引:0
The data refer to the monthly water consumption in the Neapolitan area over more than a 30 year period. The model proposed makes it possible to separate the trend in the water consumption time series from the seasonal fluctuation characterized by monthly peak coefficients with residual component. An ARMA (1,1) model has been used to fit the residual component process. Furthermore, the availability of daily water consumption data for a three-year period allows the calculation of the daily peak coefficients for each month, and makes it possible to determine future water demand on the day of peak water consumption.Notation
j
numerical order of the month in the year
-
i
numerical order of the year in the time series
-
t
numerical order of the month in the time series
-
h
numerical order of the month in the sequence of measured and predicted consumption values after the final stage t of the observation period
-
Z
ji
effective monthly water consumption in the month j in the year i (expressed as m3/day)
-
T
ji
predicted monthly water consumption in the month j in the year i minus the seasonal and stochastic component (expressed as m3/day)
-
C
ji
monthly peak coefficient
-
E
ji
stochastic component of the monthly water consumption in the month of j in the year i
-
Z
i
water consumption in the year i (expressed as m3/year)
-
Z
j
(t)
water consumption in the month j during the observation period (expressed as m3/day)
-
evaluation of the correlation coefficient
-
Z
j
(t)
water consumption in the month j during the observation period minus the trend
-
Y
t
transformed stochastic component from E
t
: Y
t
=ln Et
-
Y
t+h
measured value of stochastic component for t+h period after the final stage t of the observation period
-
Y
t
(h)
predicted value of stochastic component for t+h period after the final stage t of the observation period
- j
transformation coefficients from the ARMA process (m, n) to the MA () process 相似文献
8.
The general soil conservation service curve number (SCS-CN)-based Mishra and Singh (Mishra and Singh, 1999, J. Hydrologic. Eng. ASCE, 4(3), 257–264) model and its eight variants were investigated for their field applicability using a large set of rainfall-runoff events, derived from a number of U.S. watersheds varying in size from 0.3 to 30351.5 ha, grouped into five classes based on the rainfall magnitude. The analysis based on the goodness of fit criteria of root mean square error (RMSE) and error in computed and observed mean runoff revealed that the performance of the existing version of the SCS-CN method was significantly poorer than that of all the model variants on all the five data sets with rainfall 38.1 mm. The existing version showed a consistently improved performance on the data with increasing rainfall amount, but greater than 38.1 mm. The one-parameter modified SCS-CN method (a = 0.5 and = a median value) performed significantly better than the existing one on all the data sets, but far better on rainfall data less than 2 inches. Finally, the former with = 0 was recommended for routine field applications to any data set. 相似文献
9.
L. F. Barmin T. K. Kruglova V. P. Sinitsyn 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2005,39(1):44-46
Results of the use of automatic hydrogen-content meter for controlling the parameter of hydrogen in the primary coolant circuit of the Kola nuclear power plant are presented. It is shown that the correlation between the hydrogen parameter in the coolant and the hydrazine parameter in the makeup water can be used for controlling the water chemistry of the primary coolant system, which should make it possible to optimize the water chemistry at different power levelsTranslated from Élektricheskie Stantsii, No. 12, December 2004, pp. 31 – 33. 相似文献
10.
Andrzej Karbowski 《Water Resources Management》1993,7(3):207-223
This article presents the formal analysis of a problem of the optimal flood control in systems of serially connected multiple water reservoirs. It is assumed, that the basic goal is minimization of the peak flow measured at a point (cross-section) located downstream from all reservoirs and that inflows to the system are deterministic. A theorem expressing sufficient conditions of optimality for combinations of releases from the reservoirs is presented together with the relevant proof. The main features of the optimal combinations of controls are thoroughly explained. Afterwards, two methods of determining the optimal releases are presented. Finally, the results of the application of the proposed methodology to a small, four reservoir system are presented.Notations
c
i
contribution of theith,i=1, ...,m, reservoir to the total storage capacity of the multireservoir system
-
d
i
(t)
one of the uncontrolled inflows to the cascade at timet (fori=1 main inflow to the cascade, fori=2, ...,m, side inflow to theith reservoir, fori=m+1 side inflow at pointP)
-
total inflow to theith reservoir,i=2, ...,m, at timet (i.e., inflowd
i
augmented with properly delayed releaser
i–1 from the previous reservoir) (used only in figures)
-
d(t),d
S
(t)
(the first term is used in text, the second one in figures) aggregated inflow to the cascade (natural flow at pointP) at timet
-
time derivative of the aggregated inflow at timet
-
i
reservoir index
-
m
number of reservoirs in cascade
-
P
control point, flood damage center
-
minimal peak of the flow at pointP (cutting level)
-
Q
p
(t)
flow measured at pointP at timet
-
flow measured at pointP at timet, corresponding to the optimal control of the cascade
-
r
i
(t)
release from theith reservoir at timet, i=1, ...,m
-
optimal release from theith reservoir at timet, i=1, ...,m
-
r
1
*
(t)
a certain release from theith reservoir at timet, different than
,i=1, ...,m, (used only in the proof of Theorem 1)
-
a piece of the optimal release from themth reservoir outside period
at timet
-
assumed storage of theith reservoir at time
(used only in the proof of Theorem 1)
-
s
i
(t)
storage of theith reservoir at timet, i=1, ...,m
-
time derivative of the storage of theith reservoir at timet, i=1, ...,m
-
storage capacity of theith reservoir,i=1, ...,m
-
(the first term is used in text, the second one in figures) total storage capacity of the cascade of reservoirs
-
S*
sum of storages, caused by implementingr
i
*
,i=1, ...,m, of all reservoirs measured at
(used only in the proof of Theorem 1)
-
t
time variable (continuous)
-
t
0
initial time of the control horizon
-
t
a
initial time of the period of constant flow equal
at pointP
-
initial time of the period of the essential filling of theith reservoir,i=1, ...,m (used only in the proof of Theorem 1)
-
t
b
final time of the period of constant flow equal
at pointP
-
final time of the period of the essential filling of theith reservoir,i=1, ...,m (used only in the proof of Theorem 1)
-
time of filling up of theith reservoir while applying method with switching of the active reservoir
-
t
f
final time of the control horizon
-
fori=1, ...,m–1, time lag betweenith andi+1th reservoir; fori=m time lag between the lowest reservoir of the cascade and the control pointP 相似文献
11.
The irrigation in regions of brackish groundwater in many parts of the world results in the rise of the water-table very close to the groundsurface. The salinity of the productive soils is therefore increased. A proper layout of the ditch-drainage system and the prediction of the spatio-temporal variation of the water table under such conditions are of crucial importance in order to control the undesirable growth of the water-table. In this paper, an approximate solution of the nonlinear Boussinesq equation has been derived to describe the water-table variations in a ditch-drainage system with a random initial condition and transient recharge. The applications of the solution is discussed with the help of a synthetic example.Notations
a
lower value of the random variable representing the initial water-table height at the groundwater divide
-
a+b
upper value of the random variable representing the initial water-table height at the groundwater divide
-
h
variable water-table height measured from the base of the aquifer
-
K
hydraulic conductivity
-
L
half width between ditches
-
m
0
initial water-table height at the groundwater divide
-
N(t)
rate of transient recharge at time t
-
N
0
initial rate of transient recharge
-
P
N
0/K
-
S
Specific yield
-
t
time of observation
-
t
0
logarithmic decrement of the recharge function
-
T
Kt/SL
-
x
distance measured from the ditch boundary
-
X
x/L
-
Y
h/L
- Y
mean of Y
- Y
Variance of Y 相似文献
12.
Dam-Break flood forecasting in Piemonte region,northwest Italy 总被引:1,自引:0,他引:1
Six major reservoirs in Piemonte region, northwest Italy, have been examined in order to assess the possible flood damages to the downstream area. In this paper, some results of the hydraulic study are presented. The floods are simulated by computer models with the input data which describe the imagined dam-break events as well as other facts. Some important practical aspects of the work are extensively discussed, i.e. the problems concerning determination of the dam-breaches, the influence of the breach parameters, and estimation of the hydraulic resistance factors.Notation A =
cross sectional area of water flow
- C =
Chezy roughness coefficient
- C =
discharge coefficient
- g =
acceleration due to gravity
- H =
height of dam-breach
- H =
height of dam
- h =
water surface level above the datum plane
- L =
width of dam
- Q =
flow discharge
- Qe, Qu =
inflow and outflow discharges respectively
- q =
lateral inflow discharge
- R* =
hydraulic radius
- T =
formation time of dam-breach
- t =
time
- V =
volume of reservoir storage
- W =
width of dam-breach
- X =
downstream distance from a dam along the river
- =
velocity distribution factor 相似文献
13.
A new approach using input-output techniques is proposed for the analysis of urban stormwater pollution caused by urban land development. The input-output model provides projections of sectoral outputs within an urban region. By defining land as an input to production, these output projections may be translated into projections of commercial and industrial land development. Furthermore, the closed version of the input-output model is used to project residential land development as a function of projected wage income. The pollutant generation in urban stormwater is related to the quantity of each category of land development by a pollutant coefficient matrix. Thus, the model can be used to predict the impact of various economic growth scenarios on pollution loadings in runoff water. This will help planners in assessing the environmental costs of various scenarios, and in preparing for remedial actions. A numerical example is provided to illustrate the applications of the model. 相似文献
14.
Time-independent (or steady-state) cases of planar (overland) flow were treated. Errors of the kinematic-wave and diffusion-wave approximations were derived for three types of boundary conditions: zero flow at the upstream end, and critical flow depth and zero depth-gradient at the downstream end. The diffusion wave approximation was found to be in excellent agreement with the dynamic wave approximation, with error in the range of 1–2% for values ofKF
0
2
(7.5). Even for small values ofKF
2
0
(e.g.,KF
2
0
=0.75), the errors were typically in the range of 11–15%. The accuracy of the diffusion wave approximation was greatly influenced by the downstream boundary condition. The error of the kinematic wave approximation was found to vary from 7 to 13% in the regions 0.05x0.95 forKF
0
2
=0.75 and was greater than 30% forKF
0
2
=0.75. 相似文献
15.
G. D. Barinberg A. E. Valamin 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2005,39(1):33-37
Design features and efficiency of some steam turbines produced at present by a plant formed as a result of division of the Turbine Motor Plant Company into several enterprises are presented.Translated from Élektricheskie Stantsii, No. 11, November 2004, pp. 27 – 32. 相似文献
16.
Optimization-simulation models were used for the systems analysis of a water resources system. The Karjan Irrigation reservoir project in India was taken as the system. Two types of optimization models, i.e., linear programming, and dynamic programming (continuous and discontinuous) were used for preliminary design purposes. The simulation technique was used for further screening. The linear programming model is most suitable for finding reservoir capacity. Dynamic programming (continuous and discontinuous models) may be used for further refining the output targets and finding the possible reservoir carry-over storages, respectively. The simulation should then be used to obtain the near optimum values of the design variables.Notations
a
1
Unit irrigation benefit [Rs.105 L–3]
-
B
1
Gross annual irrigation benefit [Rs.105]
-
B
1,t
Gross irrigation benefit in periodt [Rs.105]
-
C
1
Annual capital cost of irrigation [Rs.105]
-
C
1
Annual capital cost function for irrigation [Rs.105 L–3]
-
C
1,t
Fraction of annual capital cost for irrigation in periodt [Rs.105]
-
C
2
Annual capital cost of reservoir [Rs.105]
-
C
2
Annual capital cost function for reservoir [Rs.105 L–3]
-
C
2,t
Fraction of annual capital cost for reservoir in periodt [Rs.105]
-
El
t
Reservoir evaporation in timet [L3]
-
f
t
Optimal return from staget [Rs.105]
-
g
t
The return function for periodt [Rs.105]
-
I
t
Catchment inflow into the reservoir in periodt [L3]
-
I
t
Water that joins the main stem just above the irrigation diversion canal in timet [L3]
-
t
Local inflow to the reservoir from the surrounding area in timet [L3]
-
Ir
Annual irrigation target [L3]
-
K
t
Proportion of annual irrigation targetIr to be diverted for irrigation in timet
-
K
t
Amount by whichK
t exceeds unity is the fraction of the end storage which is assigned to reservoir evaporation losses
-
L
Loss in irrigation benefits per unit deficit in the supply [Rs.105 L–3]
-
L
1
Lower bound on annual irrigation target,Ir [L3]
-
L
2
Lower bound on reservoir capacity,Y [L3]
-
N
Number of time periods in the planning horizon
-
O
t
Total water release from the reservoir in periodt [L3]
-
O
t
*
The optimal total water release from the reservoir in timet [L3]
-
t
Secondary water release from the reservoir in timet [L3]
-
O
t
Reservoir release to the natural channel in timet [L3]
-
Od
t
Irrigation demand in timet [L3]
-
Om
1
Annual OM cost of irrigation [Rs.105]
-
Om
1
Annual OM cost function for irrigation [Rs.105 L–3]
-
Om
1,t
Fraction of annual OM cost for irrigation in periodt [Rs.105]
-
Om
2
Annual OM cost of reservoir [Rs.105]
-
Om
2
Annual OM cost function for reservoir [Rs.105 L–3]
-
Om
2,t
Fraction of annual OM cost for reservoir in periodt [L3]
-
Omint
Lower bound onO
t in timet [L3]
-
Omaxt
Upper bound onO
t in timet [L3]
-
P
t
Precipitation directly upon reservoir in timet [L3]
-
S
t
Gross/live reservoir storage at the end of timet (gross storage in the linear program and live storage in the dynamic program) [L3]
-
S
t–1
Gross/live reservoir storage at the beginning of timet [L3]
-
t
Any time period
- Trt
Transformation function
-
U
1
Upper bound onIr [L3]
-
U
2
Upper bound onY [L3]
-
Y
Total capacity of reservoir at maximum pool level [L3]
-
Ya
Fixed active (live) capacity of the reservoir (Y-Yd) [L3]
-
Ya
t
Active (live) capacity (Ymaxt –Ymint) of the reservoir in timet [L3]
-
Yd
Dead storage of the reservoir [L3]
-
Ymaxt
Capacity up to the normal pool level of the reservoir in timet [L3]
-
Ymaxt
Live capacity up to the normal pool level of the reservoir in timet [L3]
-
Ymint
Capacity up to the minimum pool level of the reservoir in timet [L3]
-
Ymint
Live capacity up to the minimum pool level of the reservoir in timet [L3] 相似文献
17.
Using a large set of rainfall-runoff data from 234 small to large watersheds from USA, this paper evaluates the modified version of the [Mishra, S. K. and Singh, V. P., 2002a, SCS-CN-based hydrologic simulation package, in V. P. Singh and D. K. Frevert (eds), Mathematical Models in Small Watershed Hydrology, Water Resources Publications, Chap. 13, pp. 391–464] (MS) model which is based on the Soil Conservation Service Curve Number (SCS-CN) methodology and incorporates the antecedent moisture in direct surface runoff computations. Comparison with the existing SCS-CN method using the t-test and the ranking-based grading shows that the modified MS model performs far better than the existing SCS-CN model. 相似文献
18.
N. V. Tikhomirova V. D. Novozhenin 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2004,38(6):309-314
The authors describe the Vladimirskaya hydroelectric pumped storage power plant that is currently being designed as the pilot Russian power project for the 21st century.Translated from Gidrotekhnicheskoe Stroitelstvo, No. 8, August 2004, pp. 15 – 20. 相似文献
19.
Spectral Reflectance,Growth and Chlorophyll Relationships for Rice Crop in a Semi-Arid Region of India 总被引:2,自引:0,他引:2
Relations among spectral reflectance, chlorophyll a, and growth of rice plants grown on irrigated light textured soil in a semi arid region are presented here. There was a linear relation between spectral reflectance and rice plant height (r = 0.97), for band 1 (0.45–0.52 m) reflectance values. On the other hand, in bands 2 (0.52–0.60 m) and 3 (0.63–0.69 m), reflectance values decreased until 70 days after planting (DAP) and then increased during the reproductive phase of the crop. The near infrared band 4 (0.76–0.90 m) showed a maximum reflectance at 59 DAP (panicle initiation stage) and a decline in reflectance thereafter through maturity. The peak value of IR/R ratio was 16.39 at 62 DAP during the early reproductive phase; thereafter, it declines gradually with the maturity of the crop. Chlorophyll a concentration was high during early growth (vegetative and early reproductive stages) and decreased during the flowering and maturity stages. The rice plant canopy show a high chlorophyll a concentration at 64 and 59 DAP for sites A and B, respectively. Chlorophyll a concentration is higher in site A plant canopies than it is in site B during the entire crop cycle. A good inverse correlation (r = 0.91) has been found between chlorophyll a and band 1, while the IR/R ratio and the normalised difference vegetation index (NDVI) showed a relationship (r = 0.78) with the chlorophyll a concentration during the crop cycle. Band 2, 3 and 4 radiance values show a biphasic linear relationship with chlorophyll a concentrations, negative for early growth and positive for flowering and maturity stages. Results indicate that the period between 66 to 70 DAP is most suitable for the assessment of rice crop yield, based on chlorophyll a concentration. 相似文献
20.
K. P. Meskheli 《Power Technology and Engineering (formerly Hydrotechnical Construction)》1990,24(12):747-755
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The results obtained (Figs. 1, 2, and 3) make it possible, without relating the calculation to the dimensions of the sand ripples, to determine , H, and v by the method of selection using Chezy's relationship, if i, the flow rate Qa and the water temperature, the fineness of the sand, and the cross section of the water course are known (i is equated to the slope of the free surface). In this case, the average value of the exponent N in relationship (22) (N=1.05 for small water courses and hydraulic flumes, H1.0 m, and N=1.08 for large water courses, \s>1.0 m) can be assigned as its value. The calculation should be performed within the above-indicated limits of variation in and the relative start-off velocities in accordance with the following sequence: a) based on the fineness of the sand, n* can be established from the curve presented in Fig. 3; b) a number of values of the average depth H can be assigned, and the corresponding values of determined — the area of the active section, v*, R, Re*d, and from (22),
, and the flow rate
; and, c) the Q=f(H) curve from which the computed depth values Hc corresponding to the assinged flow rate Qa, and then the velocity of the flow vc can be constructed.
The error associated with the accuracy of the determination is within 5%. 相似文献
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