A. A. Alazbâ 4gricultural Engineering Deput'ufient. Calirye of lgriculture , King Saud L{niv'ersi... more A. A. Alazbâ 4gricultural Engineering Deput'ufient. Calirye of lgriculture , King Saud L{niv'ersi4,. p.it,oOL. ,\uittli Arubia ABSTRACT' Ti:e Penrnan-l\iontcilh lnodel \\as assessed for h3'pcr-arid ciinrate. rvhich prevails iu nlosi areas ol Saudi Arabia, par.ticularly in the central regions. Atso, four different tbnns of the Penma* combilration i-r'pe-equation for the estimates of alfalla refcrence e'l'apotratlspiration l,lIT,u) hare bcen investigaled. The tested models, in additi,:in to the Penman-Monteilh. includeri the Penrnan i982 Kinrbcrll'; thc Penniati i972 Kirnbcrly: the Penuran uncorrc.cted FAO-24; and the Penman equarion locally calibrated for *ind function. The results reveal tliat tire Penman-Monteith is a good estimatcr o{ ET,.,1 undcr hvper-arid conditions. f he model provided betler ET,4 prcdictions ivith modification of the leaf area index (Zl1) equation.In accordance n'ith tlre modified LAI equation" thc standard error of estimatcs (Sf$ for tire model rcduced lrom 1.59 to about i.0 rnrrr/da-v. The results also showed that the localiy calibrated Peninan model is highl,v suitahle for the central part of Saudi Arabia. I'he Pentnan 1982 and 1972 Kimberl;' models fairll estimated I7,., n ith advantageLrus to the Iater one. The Penman uncorected FAO-ll largely underestimated tlie alfalla relerence evapotranspiration andinherentl-v. has the largest SEI tlrat eqr:als 2.81 mm'dar. lt. hou'ever, was possible to reduce itŝ iEE to 0.81 mmr'dal * i1h usin,g an allalfa*grass conversion ratio of-1-2i.-55 in lir.u o1'1.15. Key v:orit : evap()tr(tnspirulion, et)ilpt)lrutnsltiration metheds, hyperarid ciittttrte.re.f'erence eyepolransltiratirsrt, Pettntun' Montcith model. Saudi,4ruhia. l.INTRODUCTION l.l.Gencral Global increase of water demand has obv'ioLtsil' hc-corre a fact duc to the rapiii increase ilr lvorid popuiation. ,{itrto't aii tri titts population increase rviil be iri the Third Woricl. uher< ih.-re at'e alreadl plenty' of'rvatei-and sanitation probients and uhcre irhr-'ut i.100 peopie {tncsth' children) die even hour dr.re tr,r *aterbortle dise ases (iltruwer. :000). I'he dernand of water that includes agriculture. municipal use. atrd indnstry. is anticipated to increase rapirlly in the dereioping cctuntries. Saudi Arat:ia, anrong t.'ther courrtries ol the Arabian Peniusula, is one of tlie coutttiies suftbring most liom rapid water demand and acute t'ater sltortage (Alazlra. 1998). lhis is altributeci to the scarcit-r oi precipitirtion and liurited water resources, in riddition to the lvatcr demand augtlentation. For agricultural purposes alone" tlre-abstraction oi' grrlund \r'aier is c:.-pected tu reach 20.i1 billior: m'and 12.2 biiiion tn'in the lcars 2000 and 2010. respec'rireiv" (AbduL'azzak. 199-.i. Thi-< anticipatcd iiuge increase in agricLiltural definltcir encourages ef ficicirt use of thc irrigation rvater thal is apparentl\ accountil]g tbr 9C 9'o oi the totai consuined agricuitula! $ater. fhe cftlcient usc r-'f thc rn"igation \iater can onir' tre accr-rnrplished throLrgh pitrper rnigati,:n prt-ject planrrlng altd management. Ihe proper prlanninr an.l nlanasclltent of thr' irriqation projects iuvolvc various aspects ant] nur.t-'irt,Lts iaci.-rs sLirir ',r.inter rvheai (Triticum ae\!iyum L.) at Bushland, Texas. in the semiarid Southern High Piains for the 1989-i990. 1991-1992and l99Z-1993 rvinter nheat .rLrpping scasons using rveiuiring lvsirneters.
Abstract. The water uniformity for a center pivot system has been investigated. The uniformity of... more Abstract. The water uniformity for a center pivot system has been investigated. The uniformity of above and below soil surface was evaluated along the main line and in the direction of the system movement. Three sprinklers' heights, which were 50, 100 and 130 cm, have been ...
Journal of Irrigation and Drainage Engineering, 2001
... CE Database Search | Descriptions | Search Tips | Subject Heading List. Closure of &quot;... more ... CE Database Search | Descriptions | Search Tips | Subject Heading List. Closure of &quot;Explicit Volume Balance Model Solution&quot;. See original paper by AA Alazba , AMASCE , (Asst. Prof., Dept. of Agric. Engrg., King Saudi Univ., Riyadh, Saudi Arabia, 11451. ...
Based on the technique of geographical information systems (GIS), a computer program was develope... more Based on the technique of geographical information systems (GIS), a computer program was developed to estimate the irrigation water requirements in the Kingdom of Saudi Arabia (KSA). Consecutively, the basic elements and fundamental information and data were ...
Precisely determined evapotranspiration (ET) is necessary for maximization of water beneficiary u... more Precisely determined evapotranspiration (ET) is necessary for maximization of water beneficiary use and hydrologic applications, particularly in arid and semiarid regions where water source is so limited, such as Saudi Arabia. Evapotranspiration is a complex, nonlinear process. However, data driven techniques can be used model it without requiring a complete understanding of the physics involved. Therefore, the Artificial Neural Networks (ANN) technique was used to estimate the daily reference evapotranspiration (ETref). Eight combinations of eight climatic parameters and crop height were used as input. The daily climatic variables were collected by 13 meteorological stations from 1980 to 2010. The ANN models were trained on 65% of the climatic data and tested using the remaining 35%. The generalised Penman-Monteith (PMG) model was used as a reference target for evapotranspiration values, with hc varies from 5 to 105 cm with increment of a centimeter. The developed models were spati...
GEP was invented by Ferreira [12] and is the natu ral development of genetic algorithms and genet... more GEP was invented by Ferreira [12] and is the natu ral development of genetic algorithms and genetic programming. GEP has been applied in fields as diverse as artificial intelligence, artificial life, engi neering and science, financial markets, industrial, chemical and biological processes and mechanical
Paper No. 042092 An ASAE Meeting Presentation ... COMPARISON OF THE ASCE STANDARDIZED AND OTHER P... more Paper No. 042092 An ASAE Meeting Presentation ... COMPARISON OF THE ASCE STANDARDIZED AND OTHER PENMAN-MONTEITH TYPE EQUATIONS UNDER HYPER-ARID AREA. ... AA Alazba Associate Professor King Saud University Agricultural Engineering Department ...
Artificial neural networks (ANNs) and gene expression programming (GEP) were compared to estimate... more Artificial neural networks (ANNs) and gene expression programming (GEP) were compared to estimate daily reference evapotranspiration (ET ref) under arid conditions. The daily climatic variables were collected by 13 meteorological stations from 1980 to 2010. The ANN and GEP models were trained on 65% of the climatic data and tested using the remaining 35%. The generalised Penman-Monteith (PMG) model was used as a reference target for evapotranspiration values, with h c varies from 5 to 105 cm with increment of a centimetre. The developed models were spatially validated using climatic data from 1980 to 2010 taken from another six meteorological stations. The results showed that the eight ET ref models developed using the ANN technique were slightly more accurate than those developed using the GEP technique. The ANN models' determination coefficients (R 2) ranged from 67.6% to 99.8% and root mean square error (RMSE) values ranged from 0.20 to 2.95 mm d-1. The GEP models' R 2 values ranged from 64.4% to 95.5% and RMSE values ranged from 1.13 to 3.1 mm d-1. Although the GEP models performed slightly worse than the ANN models, the GEP models used explicit equations.
Drought forecasting plays a crucial role in drought mitigation actions. Thus, this research deals... more Drought forecasting plays a crucial role in drought mitigation actions. Thus, this research deals with linear stochastic models (autoregressive integrated moving average (ARIMA)) as a suitable tool to forecast drought. Several ARIMA models are developed for drought forecasting using the Standardized Precipitation Evapotranspiration Index (SPEI) in a hyper-arid climate. The results reveal that all developed ARIMA models demonstrate the potential ability to forecast drought over different time scales. In these models, the p, d, q, P, D and Q values are quite similar for the same SPEI time scale. This is in correspondence with autoregressive (AR) and moving average (MA) parameter estimate values, which are also similar. Therefore, the ARIMA model (1, 1, 0) (2, 0, 1) could be considered as a general model for the Al Qassim region. Meanwhile, the ARIMA model (1, 0, 3) (0, 0, 0) at 3-SPEI and the ARIMA model (1, 1, 1) (2, 0, 1) at 24-SPEI could be generalized for the Hail region. The ARIMA models at the 24-SPEI time scale is the best forecasting models with high R 2 (more than 0.9) and lower values of RMSE and MAE, while they are the least forecasting at the 3-SPEI time scale. Accordingly, this study recommends that ARIMA models can be very useful tools for drought forecasting that can help water resource managers and planners to take precautions considering the severity of drought in advance.
Climate variability is receiving much attention recently because it has significant effects on wa... more Climate variability is receiving much attention recently because it has significant effects on water resources and therefore on the livelihood of society especially in water scarce countries such the Kingdom of Saudi Arabia (KSA). Approach: The aim of this study was to explore changes in the reference evapotranspiration (ET o ) using data from 27 weather stations through years 1980-2008 and to identify trend directions in the ET o as an indicator to climate variability in the region. ET o was calculated using FAO-56 Penman Monteith method and trends analyses were performed with non-parametric statistics proposed by Mann-Kendall and Sen slope estimator. Results: Results indicated that the average ET o varied from 5 mm day -1 in January to more than 15 mm day -1 in July with extreme average values ranged from 4 mm day -1 in January to 18 mm day -1 in July. The trend analyses indicated that the average annual maximum and minimum daily ET o steadily increased over the study period. The ET o annual daily average had increased from about 9.6 mm day -1 in 1980 to 10.5 mm day -1 in 2008. Trend analysis with Mann-Kendall and Sen Slope gave consistent results and were able to detect trend direction and its significant level for each month and for each station. In general, most of stations showed an increasing trend especially in the Northern parts of KSA and along the longitudinal line of 45°. 'Yenbo' station showed a significant increasing trend in ET o for the entire year. The increasing trends prevailed during most of the year except in the winter months from October to January. Even during these winter months, significant decreasing trends were observed for only four stations. Conclusion: It is recommended to perform similar studies on other parts of the Arabian Peninsula using wider databases, and to consider the increasing trend of ET o in the planning for agricultural and water resources projects.
This is the second part of the companion papers assessing HYDRUS simulations of drip irrigation. ... more This is the second part of the companion papers assessing HYDRUS simulations of drip irrigation. While the first part focused on surface drip simulations, this part focused on the subsurface simulations and how they differ from the surface simulations. We evaluated the effect of different domain geometries, emission element shapes, coordinate systems, emitter discharges, and soil textures on the accuracy and stability of the simulation. The results showed that all the 2D and 3D simulations were done with a mass balance error of less than 0.9%, in contrast to the surface 2D cases that have large error values. The flux-conductivity ratio for subsurface simulations does not have the same influence on the mass balance error as in the surface simulations. We found extreme differences in the simulation speeds that were attributed to the emitter&#39;s location (the subsurface is faster), the domain axes (axisymmetric is faster than Cartesian), soil texture (the lighter is faster), the elapsed time or stage (the redistribution is hugely faster than redistribution). For the 2D-3D comparisons, we found that the 2D domains mostly underestimate the 3D slices. Finally, we found that the flux profiles of the 2D domains perfectly match the flux profiles of the 3D domains, in contrast to the surface comparisons. Hence, we can use 2D simulations reliably for subsurface drip, but not for the surface drip.
Gene Expression Programming (GEP) was used to develop new mathematical equations for estimating ... more Gene Expression Programming (GEP) was used to develop new mathematical equations for estimating daily reference evapotranspiration (ETref) for the Kingdom of Saudi Arabia. The daily climatic variables were collected by 13 meteorological stations from 1980 to 2010. The GEP models were trained on 65% of the climatic data and tested using the remaining 35%. The generalised PenmanMonteith model was used as a reference target for evapotranspiration (ET) values, with hc varies from 5 to 105 cm with increment of a centimetre. Eight GEP models have been compared with four locally calibrated traditional models (HargreavesSamani, Irmak, JensenHaise and KimberlyPenman). The results showed that the statistical performance criteria values such as determination coefficients (R2) ranged from as low as 64.4% for GEPMOD1, where the only parameters included (maximum, minimum, and mean temperature and crop height), to as high as 95.5% for GEPMOD8 with which all climatic parameters included (...
Accurate estimations of reference evapotranspiration (ET ref) are extremely important for maximiz... more Accurate estimations of reference evapotranspiration (ET ref) are extremely important for maximizing the beneficial use of water and hydrologic applications, particularly in arid and semiarid regions where water sources are so limited. The aim of this study is to develop mathematical models to calculate the daily ET ref using a gene expression programming (GEP) technique. Eight GEP models (GEP-MOD1-8) were developed from combinations of climatic variables. The Penman-Monteith equation was considered the reference method, with the reference plant height varying from 5 to 105 cm in 5-cm increments. Daily climatic variables collected from 13 meteorological stations, one station from every region within the Kingdom of Saudi Arabia, covered the 1980 to 2010 period. Of the available climatic data, 65 % was used in the training process for the eight developed GEP models, and 35 % was used in the testing process. The accuracy of the eight developed GEP models to estimate ET ref varied in significance depending on the climatic variables that were included. As more climatic parameters were input, the accuracy of the GEP model increased. For the testing process, the coefficient of determination (R 2) ranged from a low of 63.4 % for GEP-MOD1 to a high of 95.4 % for GEP-MOD8, and the root mean square error (RMSE) values ranged from 3.19 mm day −1 for GEP-MOD1 to 1.14 mm day −1 for GEP-MOD8. From the spatial evaluation, the values of RMSE ranged from 3.27 mm day − 1 for GEP-MOD1 to 1.21 mm day −1 for GEP-MOD8. In addition, the respective RMSE values resulting from GEP-MOD8 for plant heights of 50 and 12 cm were 0.75 and 0.96 cm. This implies that the developed GEP-MOD8 can be used for any value of the reference plant height ranging from 5 to 105 cm with insignificant errors. Interestingly, solar radiation had an almost insignificant effect on ET ref in the hyper-arid conditions. In contrast, wind speed and plant height had a large positive effect on increasing the accuracy of calculating ET ref .
As the temperature and the diurnal temperature range (DTR) influence our life in many fields like... more As the temperature and the diurnal temperature range (DTR) influence our life in many fields like agriculture and health, changes in either parameter may affect our current and future plans in such areas. This paper investigates the variability of temperature and DTR in the Levant and the Arabian Peninsula (172 stations in 12 countries) in different study periods of 10, 25, 40, 50, and 60 years. The data were tested for homogeneity using four standard tests, and we used the nonparametric statistics Mann-Kendall and Theil-Sen to calculate trend significance, direction, and magnitude in time series. Our results show a significant warming trend in 45–60% of the region with an average increase of 0.65, 0.43, and 0.30 °C/decade for the 25-, 40-, and 50-year study periods. The highest number of stations that have a significant increase in temperature occurs in spring and summer. On the other hand, decreasing DTR trends occur in about 31% of the region, mostly in the south of the Arabian Peninsula at 0.60 °C/decade. This work, additionally, provides an interactive online tool that shows the trends and temperature on zoomable maps, charts, and other visuals to station level. This tool could benefit researchers and strategic planners for the studied region. In many stations, we found that there are a significant increase in temperature and a decrease in DTR which reflect a severe change in the climate that should be considered in future planning. We recommend expanding this study to cover precipitation and other meteorological factors.
This study investigates the ability of gene expression programming (GEP) in modeling of the infil... more This study investigates the ability of gene expression programming (GEP) in modeling of the infiltrated water volume (Z) under furrow irrigation. Field data were collected in the literature study for modeling Z covering wide range of opportunity time. Five variables were used as input parameters; inflow rate (Q o), furrow length (L), waterfront advance time at the end of the furrow (T L), infiltration opportunity time (T o) and cross-sectional area of the inflow (A o). The following statistical parameters that coefficient of determination (R 2), overall index of the model performance (OI), root mean square errors (RMSE) and mean absolute errors (MAE) are used as comparing criteria for the evaluation of the models' performances. The best value of the statistical parameters which range in training, testing and validation processes as the following (R 2 = 95-97%; OI = 94-97%; RMSE = 0.013-0.009 m 3 m À1 ; and MAE = 0.011-0.007 m 3 m À1) implies that the GEP model provides an excellent fit for the measured data. A comparison is made between the estimates provided by the GEP and the two-point method. The comparison results reveal that the GEP models are superior to two-point method. Furthermore, the remarkable advantage of GEP was that it resulted in an explicit equation for the estimation of the Z under furrow irrigation.
Paper No. 042092 An ASAE Meeting Presentation ... COMPARISON OF THE ASCE STANDARDIZED AND OTHER P... more Paper No. 042092 An ASAE Meeting Presentation ... COMPARISON OF THE ASCE STANDARDIZED AND OTHER PENMAN-MONTEITH TYPE EQUATIONS UNDER HYPER-ARID AREA. ... AA Alazba Associate Professor King Saud University Agricultural Engineering Department ...
Friction head loss equations and friction correction factors were evaluated and compared to field... more Friction head loss equations and friction correction factors were evaluated and compared to field observations collected from thirty center‐pivots with laterals made of PVCs. The friction head loss equations include Darcy‐Weisbach (D‐W), Hazen‐Williams (H‐W), and Scobey, in addition to a proposed equation valid for smooth and rough pipe types and for all turbulent flow types. The proposed equation was developed by combing the equations of D‐W and H‐W, along with the multiple non‐linear regression technique. The friction correction factors were computed using the typical Christiansen, modified Christiansen, Anwar, and Alazba formulae. The evaluation has been based on statistical error techniques with observed values as a reference. With the combination of modified Christiansen, Anwar, and Alazba formulae, the results revealed that the magnitudes of friction head loss calculated using D‐W equation, H‐W equation, and proposed equation were in agreement with field observations. The root...
A. A. Alazbâ 4gricultural Engineering Deput'ufient. Calirye of lgriculture , King Saud L{niv'ersi... more A. A. Alazbâ 4gricultural Engineering Deput'ufient. Calirye of lgriculture , King Saud L{niv'ersi4,. p.it,oOL. ,\uittli Arubia ABSTRACT' Ti:e Penrnan-l\iontcilh lnodel \\as assessed for h3'pcr-arid ciinrate. rvhich prevails iu nlosi areas ol Saudi Arabia, par.ticularly in the central regions. Atso, four different tbnns of the Penma* combilration i-r'pe-equation for the estimates of alfalla refcrence e'l'apotratlspiration l,lIT,u) hare bcen investigaled. The tested models, in additi,:in to the Penman-Monteilh. includeri the Penrnan i982 Kinrbcrll'; thc Penniati i972 Kirnbcrly: the Penuran uncorrc.cted FAO-24; and the Penman equarion locally calibrated for *ind function. The results reveal tliat tire Penman-Monteith is a good estimatcr o{ ET,.,1 undcr hvper-arid conditions. f he model provided betler ET,4 prcdictions ivith modification of the leaf area index (Zl1) equation.In accordance n'ith tlre modified LAI equation" thc standard error of estimatcs (Sf$ for tire model rcduced lrom 1.59 to about i.0 rnrrr/da-v. The results also showed that the localiy calibrated Peninan model is highl,v suitahle for the central part of Saudi Arabia. I'he Pentnan 1982 and 1972 Kimberl;' models fairll estimated I7,., n ith advantageLrus to the Iater one. The Penman uncorected FAO-ll largely underestimated tlie alfalla relerence evapotranspiration andinherentl-v. has the largest SEI tlrat eqr:als 2.81 mm'dar. lt. hou'ever, was possible to reduce itŝ iEE to 0.81 mmr'dal * i1h usin,g an allalfa*grass conversion ratio of-1-2i.-55 in lir.u o1'1.15. Key v:orit : evap()tr(tnspirulion, et)ilpt)lrutnsltiration metheds, hyperarid ciittttrte.re.f'erence eyepolransltiratirsrt, Pettntun' Montcith model. Saudi,4ruhia. l.INTRODUCTION l.l.Gencral Global increase of water demand has obv'ioLtsil' hc-corre a fact duc to the rapiii increase ilr lvorid popuiation. ,{itrto't aii tri titts population increase rviil be iri the Third Woricl. uher< ih.-re at'e alreadl plenty' of'rvatei-and sanitation probients and uhcre irhr-'ut i.100 peopie {tncsth' children) die even hour dr.re tr,r *aterbortle dise ases (iltruwer. :000). I'he dernand of water that includes agriculture. municipal use. atrd indnstry. is anticipated to increase rapirlly in the dereioping cctuntries. Saudi Arat:ia, anrong t.'ther courrtries ol the Arabian Peniusula, is one of tlie coutttiies suftbring most liom rapid water demand and acute t'ater sltortage (Alazlra. 1998). lhis is altributeci to the scarcit-r oi precipitirtion and liurited water resources, in riddition to the lvatcr demand augtlentation. For agricultural purposes alone" tlre-abstraction oi' grrlund \r'aier is c:.-pected tu reach 20.i1 billior: m'and 12.2 biiiion tn'in the lcars 2000 and 2010. respec'rireiv" (AbduL'azzak. 199-.i. Thi-< anticipatcd iiuge increase in agricLiltural definltcir encourages ef ficicirt use of thc irrigation rvater thal is apparentl\ accountil]g tbr 9C 9'o oi the totai consuined agricuitula! $ater. fhe cftlcient usc r-'f thc rn"igation \iater can onir' tre accr-rnrplished throLrgh pitrper rnigati,:n prt-ject planrrlng altd management. Ihe proper prlanninr an.l nlanasclltent of thr' irriqation projects iuvolvc various aspects ant] nur.t-'irt,Lts iaci.-rs sLirir ',r.inter rvheai (Triticum ae\!iyum L.) at Bushland, Texas. in the semiarid Southern High Piains for the 1989-i990. 1991-1992and l99Z-1993 rvinter nheat .rLrpping scasons using rveiuiring lvsirneters.
Abstract. The water uniformity for a center pivot system has been investigated. The uniformity of... more Abstract. The water uniformity for a center pivot system has been investigated. The uniformity of above and below soil surface was evaluated along the main line and in the direction of the system movement. Three sprinklers' heights, which were 50, 100 and 130 cm, have been ...
Journal of Irrigation and Drainage Engineering, 2001
... CE Database Search | Descriptions | Search Tips | Subject Heading List. Closure of &quot;... more ... CE Database Search | Descriptions | Search Tips | Subject Heading List. Closure of &quot;Explicit Volume Balance Model Solution&quot;. See original paper by AA Alazba , AMASCE , (Asst. Prof., Dept. of Agric. Engrg., King Saudi Univ., Riyadh, Saudi Arabia, 11451. ...
Based on the technique of geographical information systems (GIS), a computer program was develope... more Based on the technique of geographical information systems (GIS), a computer program was developed to estimate the irrigation water requirements in the Kingdom of Saudi Arabia (KSA). Consecutively, the basic elements and fundamental information and data were ...
Precisely determined evapotranspiration (ET) is necessary for maximization of water beneficiary u... more Precisely determined evapotranspiration (ET) is necessary for maximization of water beneficiary use and hydrologic applications, particularly in arid and semiarid regions where water source is so limited, such as Saudi Arabia. Evapotranspiration is a complex, nonlinear process. However, data driven techniques can be used model it without requiring a complete understanding of the physics involved. Therefore, the Artificial Neural Networks (ANN) technique was used to estimate the daily reference evapotranspiration (ETref). Eight combinations of eight climatic parameters and crop height were used as input. The daily climatic variables were collected by 13 meteorological stations from 1980 to 2010. The ANN models were trained on 65% of the climatic data and tested using the remaining 35%. The generalised Penman-Monteith (PMG) model was used as a reference target for evapotranspiration values, with hc varies from 5 to 105 cm with increment of a centimeter. The developed models were spati...
GEP was invented by Ferreira [12] and is the natu ral development of genetic algorithms and genet... more GEP was invented by Ferreira [12] and is the natu ral development of genetic algorithms and genetic programming. GEP has been applied in fields as diverse as artificial intelligence, artificial life, engi neering and science, financial markets, industrial, chemical and biological processes and mechanical
Paper No. 042092 An ASAE Meeting Presentation ... COMPARISON OF THE ASCE STANDARDIZED AND OTHER P... more Paper No. 042092 An ASAE Meeting Presentation ... COMPARISON OF THE ASCE STANDARDIZED AND OTHER PENMAN-MONTEITH TYPE EQUATIONS UNDER HYPER-ARID AREA. ... AA Alazba Associate Professor King Saud University Agricultural Engineering Department ...
Artificial neural networks (ANNs) and gene expression programming (GEP) were compared to estimate... more Artificial neural networks (ANNs) and gene expression programming (GEP) were compared to estimate daily reference evapotranspiration (ET ref) under arid conditions. The daily climatic variables were collected by 13 meteorological stations from 1980 to 2010. The ANN and GEP models were trained on 65% of the climatic data and tested using the remaining 35%. The generalised Penman-Monteith (PMG) model was used as a reference target for evapotranspiration values, with h c varies from 5 to 105 cm with increment of a centimetre. The developed models were spatially validated using climatic data from 1980 to 2010 taken from another six meteorological stations. The results showed that the eight ET ref models developed using the ANN technique were slightly more accurate than those developed using the GEP technique. The ANN models' determination coefficients (R 2) ranged from 67.6% to 99.8% and root mean square error (RMSE) values ranged from 0.20 to 2.95 mm d-1. The GEP models' R 2 values ranged from 64.4% to 95.5% and RMSE values ranged from 1.13 to 3.1 mm d-1. Although the GEP models performed slightly worse than the ANN models, the GEP models used explicit equations.
Drought forecasting plays a crucial role in drought mitigation actions. Thus, this research deals... more Drought forecasting plays a crucial role in drought mitigation actions. Thus, this research deals with linear stochastic models (autoregressive integrated moving average (ARIMA)) as a suitable tool to forecast drought. Several ARIMA models are developed for drought forecasting using the Standardized Precipitation Evapotranspiration Index (SPEI) in a hyper-arid climate. The results reveal that all developed ARIMA models demonstrate the potential ability to forecast drought over different time scales. In these models, the p, d, q, P, D and Q values are quite similar for the same SPEI time scale. This is in correspondence with autoregressive (AR) and moving average (MA) parameter estimate values, which are also similar. Therefore, the ARIMA model (1, 1, 0) (2, 0, 1) could be considered as a general model for the Al Qassim region. Meanwhile, the ARIMA model (1, 0, 3) (0, 0, 0) at 3-SPEI and the ARIMA model (1, 1, 1) (2, 0, 1) at 24-SPEI could be generalized for the Hail region. The ARIMA models at the 24-SPEI time scale is the best forecasting models with high R 2 (more than 0.9) and lower values of RMSE and MAE, while they are the least forecasting at the 3-SPEI time scale. Accordingly, this study recommends that ARIMA models can be very useful tools for drought forecasting that can help water resource managers and planners to take precautions considering the severity of drought in advance.
Climate variability is receiving much attention recently because it has significant effects on wa... more Climate variability is receiving much attention recently because it has significant effects on water resources and therefore on the livelihood of society especially in water scarce countries such the Kingdom of Saudi Arabia (KSA). Approach: The aim of this study was to explore changes in the reference evapotranspiration (ET o ) using data from 27 weather stations through years 1980-2008 and to identify trend directions in the ET o as an indicator to climate variability in the region. ET o was calculated using FAO-56 Penman Monteith method and trends analyses were performed with non-parametric statistics proposed by Mann-Kendall and Sen slope estimator. Results: Results indicated that the average ET o varied from 5 mm day -1 in January to more than 15 mm day -1 in July with extreme average values ranged from 4 mm day -1 in January to 18 mm day -1 in July. The trend analyses indicated that the average annual maximum and minimum daily ET o steadily increased over the study period. The ET o annual daily average had increased from about 9.6 mm day -1 in 1980 to 10.5 mm day -1 in 2008. Trend analysis with Mann-Kendall and Sen Slope gave consistent results and were able to detect trend direction and its significant level for each month and for each station. In general, most of stations showed an increasing trend especially in the Northern parts of KSA and along the longitudinal line of 45°. 'Yenbo' station showed a significant increasing trend in ET o for the entire year. The increasing trends prevailed during most of the year except in the winter months from October to January. Even during these winter months, significant decreasing trends were observed for only four stations. Conclusion: It is recommended to perform similar studies on other parts of the Arabian Peninsula using wider databases, and to consider the increasing trend of ET o in the planning for agricultural and water resources projects.
This is the second part of the companion papers assessing HYDRUS simulations of drip irrigation. ... more This is the second part of the companion papers assessing HYDRUS simulations of drip irrigation. While the first part focused on surface drip simulations, this part focused on the subsurface simulations and how they differ from the surface simulations. We evaluated the effect of different domain geometries, emission element shapes, coordinate systems, emitter discharges, and soil textures on the accuracy and stability of the simulation. The results showed that all the 2D and 3D simulations were done with a mass balance error of less than 0.9%, in contrast to the surface 2D cases that have large error values. The flux-conductivity ratio for subsurface simulations does not have the same influence on the mass balance error as in the surface simulations. We found extreme differences in the simulation speeds that were attributed to the emitter&#39;s location (the subsurface is faster), the domain axes (axisymmetric is faster than Cartesian), soil texture (the lighter is faster), the elapsed time or stage (the redistribution is hugely faster than redistribution). For the 2D-3D comparisons, we found that the 2D domains mostly underestimate the 3D slices. Finally, we found that the flux profiles of the 2D domains perfectly match the flux profiles of the 3D domains, in contrast to the surface comparisons. Hence, we can use 2D simulations reliably for subsurface drip, but not for the surface drip.
Gene Expression Programming (GEP) was used to develop new mathematical equations for estimating ... more Gene Expression Programming (GEP) was used to develop new mathematical equations for estimating daily reference evapotranspiration (ETref) for the Kingdom of Saudi Arabia. The daily climatic variables were collected by 13 meteorological stations from 1980 to 2010. The GEP models were trained on 65% of the climatic data and tested using the remaining 35%. The generalised PenmanMonteith model was used as a reference target for evapotranspiration (ET) values, with hc varies from 5 to 105 cm with increment of a centimetre. Eight GEP models have been compared with four locally calibrated traditional models (HargreavesSamani, Irmak, JensenHaise and KimberlyPenman). The results showed that the statistical performance criteria values such as determination coefficients (R2) ranged from as low as 64.4% for GEPMOD1, where the only parameters included (maximum, minimum, and mean temperature and crop height), to as high as 95.5% for GEPMOD8 with which all climatic parameters included (...
Accurate estimations of reference evapotranspiration (ET ref) are extremely important for maximiz... more Accurate estimations of reference evapotranspiration (ET ref) are extremely important for maximizing the beneficial use of water and hydrologic applications, particularly in arid and semiarid regions where water sources are so limited. The aim of this study is to develop mathematical models to calculate the daily ET ref using a gene expression programming (GEP) technique. Eight GEP models (GEP-MOD1-8) were developed from combinations of climatic variables. The Penman-Monteith equation was considered the reference method, with the reference plant height varying from 5 to 105 cm in 5-cm increments. Daily climatic variables collected from 13 meteorological stations, one station from every region within the Kingdom of Saudi Arabia, covered the 1980 to 2010 period. Of the available climatic data, 65 % was used in the training process for the eight developed GEP models, and 35 % was used in the testing process. The accuracy of the eight developed GEP models to estimate ET ref varied in significance depending on the climatic variables that were included. As more climatic parameters were input, the accuracy of the GEP model increased. For the testing process, the coefficient of determination (R 2) ranged from a low of 63.4 % for GEP-MOD1 to a high of 95.4 % for GEP-MOD8, and the root mean square error (RMSE) values ranged from 3.19 mm day −1 for GEP-MOD1 to 1.14 mm day −1 for GEP-MOD8. From the spatial evaluation, the values of RMSE ranged from 3.27 mm day − 1 for GEP-MOD1 to 1.21 mm day −1 for GEP-MOD8. In addition, the respective RMSE values resulting from GEP-MOD8 for plant heights of 50 and 12 cm were 0.75 and 0.96 cm. This implies that the developed GEP-MOD8 can be used for any value of the reference plant height ranging from 5 to 105 cm with insignificant errors. Interestingly, solar radiation had an almost insignificant effect on ET ref in the hyper-arid conditions. In contrast, wind speed and plant height had a large positive effect on increasing the accuracy of calculating ET ref .
As the temperature and the diurnal temperature range (DTR) influence our life in many fields like... more As the temperature and the diurnal temperature range (DTR) influence our life in many fields like agriculture and health, changes in either parameter may affect our current and future plans in such areas. This paper investigates the variability of temperature and DTR in the Levant and the Arabian Peninsula (172 stations in 12 countries) in different study periods of 10, 25, 40, 50, and 60 years. The data were tested for homogeneity using four standard tests, and we used the nonparametric statistics Mann-Kendall and Theil-Sen to calculate trend significance, direction, and magnitude in time series. Our results show a significant warming trend in 45–60% of the region with an average increase of 0.65, 0.43, and 0.30 °C/decade for the 25-, 40-, and 50-year study periods. The highest number of stations that have a significant increase in temperature occurs in spring and summer. On the other hand, decreasing DTR trends occur in about 31% of the region, mostly in the south of the Arabian Peninsula at 0.60 °C/decade. This work, additionally, provides an interactive online tool that shows the trends and temperature on zoomable maps, charts, and other visuals to station level. This tool could benefit researchers and strategic planners for the studied region. In many stations, we found that there are a significant increase in temperature and a decrease in DTR which reflect a severe change in the climate that should be considered in future planning. We recommend expanding this study to cover precipitation and other meteorological factors.
This study investigates the ability of gene expression programming (GEP) in modeling of the infil... more This study investigates the ability of gene expression programming (GEP) in modeling of the infiltrated water volume (Z) under furrow irrigation. Field data were collected in the literature study for modeling Z covering wide range of opportunity time. Five variables were used as input parameters; inflow rate (Q o), furrow length (L), waterfront advance time at the end of the furrow (T L), infiltration opportunity time (T o) and cross-sectional area of the inflow (A o). The following statistical parameters that coefficient of determination (R 2), overall index of the model performance (OI), root mean square errors (RMSE) and mean absolute errors (MAE) are used as comparing criteria for the evaluation of the models' performances. The best value of the statistical parameters which range in training, testing and validation processes as the following (R 2 = 95-97%; OI = 94-97%; RMSE = 0.013-0.009 m 3 m À1 ; and MAE = 0.011-0.007 m 3 m À1) implies that the GEP model provides an excellent fit for the measured data. A comparison is made between the estimates provided by the GEP and the two-point method. The comparison results reveal that the GEP models are superior to two-point method. Furthermore, the remarkable advantage of GEP was that it resulted in an explicit equation for the estimation of the Z under furrow irrigation.
Paper No. 042092 An ASAE Meeting Presentation ... COMPARISON OF THE ASCE STANDARDIZED AND OTHER P... more Paper No. 042092 An ASAE Meeting Presentation ... COMPARISON OF THE ASCE STANDARDIZED AND OTHER PENMAN-MONTEITH TYPE EQUATIONS UNDER HYPER-ARID AREA. ... AA Alazba Associate Professor King Saud University Agricultural Engineering Department ...
Friction head loss equations and friction correction factors were evaluated and compared to field... more Friction head loss equations and friction correction factors were evaluated and compared to field observations collected from thirty center‐pivots with laterals made of PVCs. The friction head loss equations include Darcy‐Weisbach (D‐W), Hazen‐Williams (H‐W), and Scobey, in addition to a proposed equation valid for smooth and rough pipe types and for all turbulent flow types. The proposed equation was developed by combing the equations of D‐W and H‐W, along with the multiple non‐linear regression technique. The friction correction factors were computed using the typical Christiansen, modified Christiansen, Anwar, and Alazba formulae. The evaluation has been based on statistical error techniques with observed values as a reference. With the combination of modified Christiansen, Anwar, and Alazba formulae, the results revealed that the magnitudes of friction head loss calculated using D‐W equation, H‐W equation, and proposed equation were in agreement with field observations. The root...
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