Due to the lack of standard Agro-climatic Weather Stations (AWS) in Saudi Arabia, simple conversi... more Due to the lack of standard Agro-climatic Weather Stations (AWS) in Saudi Arabia, simple conversion formulas were derived to find the average daily ETo value per month for 29 weather stations. The Hargreaves (HRG) formula was used instead of the Penman-Monteith formula due to the ease of calculation of HRG formula, as it almost require only temperature. For each station, two formulas were derived considering both standard and non-standard AWS. Results show very good statistical representation of the formulas, with average root mean squared deviations of 0.73 and 0.57 and the mean percent errors of 1.22%, and 1.12% while considering the standard and non-standard AWS, respectively. Results also confirm the importance of temperature correction when using data from non-standard AWS, especially for the stations in the Middle to Midwest region (e.g. Arriadh, AlQassim, and Almadina); where the errors of using non-standard AWS data may be up to +24% of the correct ETo value, which results in a massive waste of water.
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 mean square deviation (RMSD) values were found to be ranging from 1.6 to 1.7 m. As expected and when the typical Christiansen friction correction factor was used with the D‐W equation, with the H‐W equation, and with the proposed equation, the results showed poor agreement between observed and computed friction head loss values. This was clearly reflected by the high RMSD values that were ranging from 5.4 to 5.8 m. On the other hand, there was agreement between observed friction head loss values and those calculated using Scobey equation, invalid for PVC pipe type, when combined with the typical Christiansen formula. This interesting finding led to improved results of Scobey equation through a developed Cs coefficient suitably valid for PVC pipe type via analytically mathematical derivation. And accordingly, the RMSD value dropped from about 8.6 to 1.6 m.
Water management in Saudi Arabia is facing major challenges due to the limited water resources an... more Water management in Saudi Arabia is facing major challenges due to the limited water resources and increasing uncertainties caused by climate change. This paper presents an analysis of the daily, monthly and annual mean, maximum and total rainfall records of the Saudi meteorological data for nineteen cities covering the all thirteen districts for more than three decades (1980 to 2010). An increased annual total and maximum rainfall was observed for 6 cities with the decreased trends in both parameters for the same number of cities. For the reaming seven cities, however, an increased annual maximum rainfall trend was seen in opposite to the decreased annual total rainfall. This opposite rainfall trend is also seen for the 12 months of the year for the same city which signifies the variability of changing climate pattern not only in different districts but also during the year. The increased rain intensities due to climate change results in flooding of short in urban centers which are designed based on dry climates. Finally, the recommendations are made for the rooftop rainwater harvesting and management to cope with the increasing short-duration floods and to provide an additional source of drinking water. Co-operations among official efforts, local NGOs and public are suggested for better results of water supply management due to rainwater harvesting in Saudi Arabia in a changing climate associated with increased rainfall intensities.
Water management in Saudi Arabia is facing major challenges due to the limited water resources an... more Water management in Saudi Arabia is facing major challenges due to the limited water resources and increasing uncertainties caused by climate change. This paper presents an analysis of the daily, monthly and annual mean, maximum and total rainfall records of the Saudi meteorological data for nineteen cities covering the all thirteen districts for more than three decades (1980 to 2010). An increased annual total and maximum rainfall was observed for 6 cities with the decreased trends in both parameters for the same number of cities. For the reaming seven cities, however, an increased annual maximum rainfall trend was seen in opposite to the decreased annual total rainfall. This opposite rainfall trend is also seen for the 12 months of the year for the same city which signifies the variability of changing climate pattern not only in different districts but also during the year. The increased rain intensities due to climate change results in flooding of short in urban centers which are designed based on dry climates. Finally, the recommendations are made for the rooftop rainwater harvesting and management to cope with the increasing short-duration floods and to provide an additional source of drinking water. Co-operations among official efforts, local NGOs and public are suggested for better results of water supply management due to rainwater harvesting in Saudi Arabia in a changing climate associated with increased rainfall intensities.
Proceedings of The 4th IWA-ASPIRE Conference & Exhibition, 2011
Water Management in Saudi Arabia is facing major challenges due to the limited water resources an... more Water Management in Saudi Arabia is facing major challenges due to the limited water resources and increasing uncertainties caused by climate change. This paper presents an analysis of the daily, monthly and annual mean, maximum and total rainfall records of the Saudi meteorological data for nineteen cities covering the all thirteen districts for more than three decades. An increased annual total and maximum rainfall was observed for six cities with the decreased trends in both parameters for the same number of cities. For the reaming seven cities, however, an increased annual maximum rainfall trend was seen in opposite to the decreased annual total rainfall. This signifies the variability of changing climate pattern not in different districts but also for the different cities of the same district. This trend also highlights the increased rain intensities which results floods of short durations causing more damage to the cities. Finally, these preliminary assessments of any systematic changes in the rainfall pattern over the period 1980–2010 are viewed to demonstrate the value of rainwater harvesting as a local adaptation to climate change for sustainability of water resources in this region.
Problem statement: Reference agro-climatic Weather Stations (WS) are rarely found in newly reclai... more Problem statement: Reference agro-climatic Weather Stations (WS) are rarely found in newly reclaimed areas. The usage of weather data from non-reference WS may lead to inaccurate estimations of Evapo Transpiration (ET), especially if the non-reference stations are distant from the reclaimed location. Approach: Weather data from four WS located at Riyadh were used to calculate ET by using Penman Monteith (PM) and Hargreaves equations. PM equation was applied with both alfalfa and grass reference crops. Calculations were done with and without temperature correction for non-reference weather stations. All calculations were compared with measured lysimeter data and corrections in Hargreaves formula were suggested. Results: (1): Weather data from non-reference WS can be used safely to calculate ET only when temperature corrections are applied. (2) Hargreaves formula underestimates ET at all locations in the study area. By applying the simple linear correction to the data, highly acceptable results are obtainned. (3) The ET ratio between alfalfa and grass in Riyadh is 1.25. Conclusion: The study concluded that temperature correction for non-reference WS is essential to ensure acceptable ET calculations. Usage of Hargreaves formula is recommended with the corrections suggested in the study due to its simplicity.
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 (ETref) 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 hc varies from 5 to 105 cm with increment of a centimetre. The developed models were spatially validated using climatic data from 1980 to2010 taken from another six meteorological stations. The results showed that the eight ETref models developed using the ANN technique were slightly more accurate than those developed using the GEP technique. The ANN models’ determination coefficients (R2) 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’ R2 values ranged from64.4% 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.
A soil box was used to investigate the water movement and soil water distribution around subsurfa... more A soil box was used to investigate the water movement and soil water distribution around subsurface drip laterals with two emitters in the presence of a thin layer of polyacrylamide (PAM). Sandy soil was uniformly packed into a soil box. The PAM was applied at a rate of 29.3 kg ha-1 as a 0.01% solution by spraying it directly onto the soil surface at the required depths. With an operating pressure of 150 kPa and no PAM layer, the water consumption with a dripper line depth of 0.15 m was 12% lower than with a dripper line depth of 0.10 m. The greatest improvement in soil water-holding capacity after the addition of a PAM layer (47%) was observed when the dripper line was placed at a depth of 0.15 m under an operating pressure of 100 kPa. With a dripper line depth of 0.15 m and an operating pressure of 100 kPa, the average moisture content in the vertical planes below and above the dripper line directly increased by about 7.4 and 20%, respectively, with PAM layers at 0.25 and 0.30 m depths when compared with the moisture content with no PAM layer. The combination of a dripper line depth of 0.15 m, a PAM layer depth of 0.30 m and an operating pressure of 100 kPa will achieve optimal water management.
Identifying the shortwave solar radiation, Rs, is very important in various fields of science whi... more Identifying the shortwave solar radiation, Rs, is very important in various fields of science which is calculated by mathematical models if not measured experimentally. These models depend on the coastality factor, kr. Several equations are developed to calculate kr but with errors of estimation. The aim of this paper was to develop a local formula to calculate kr from temperature range. Based on the 30-year climate data for 29 weather stations throughout the Kingdom of Saudi Arabia (KSA), monthly temperature ranges were calculated. The hyperbolic equation was derived based on the best-fit analysis and the resulted errors of four statistical parameters were compared with any other established formula. The average of the absolute percent error was estimated as 2.1% as compared with 6–11% of the various published models. Results show that kr is inversely proportional to the distance from the coast and the altitude. In addition, it was found that urbanization has a considerable effect on kr and the noncoastal but high-population cities behaved similar as coastal cities. It is recommended to use the proposed equation due to its accuracy for the KSA instead of using other models. More research is needed to further investigate the effects of urbanization on the kr.
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 R2 (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. OPEN ACCESS
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 ...
Due to the lack of standard Agro-climatic Weather Stations (AWS) in Saudi Arabia, simple conversi... more Due to the lack of standard Agro-climatic Weather Stations (AWS) in Saudi Arabia, simple conversion formulas were derived to find the average daily ETo value per month for 29 weather stations. The Hargreaves (HRG) formula was used instead of the Penman-Monteith formula due to the ease of calculation of HRG formula, as it almost require only temperature. For each station, two formulas were derived considering both standard and non-standard AWS. Results show very good statistical representation of the formulas, with average root mean squared deviations of 0.73 and 0.57 and the mean percent errors of 1.22%, and 1.12% while considering the standard and non-standard AWS, respectively. Results also confirm the importance of temperature correction when using data from non-standard AWS, especially for the stations in the Middle to Midwest region (e.g. Arriadh, AlQassim, and Almadina); where the errors of using non-standard AWS data may be up to +24% of the correct ETo value, which results in a massive waste of water.
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 mean square deviation (RMSD) values were found to be ranging from 1.6 to 1.7 m. As expected and when the typical Christiansen friction correction factor was used with the D‐W equation, with the H‐W equation, and with the proposed equation, the results showed poor agreement between observed and computed friction head loss values. This was clearly reflected by the high RMSD values that were ranging from 5.4 to 5.8 m. On the other hand, there was agreement between observed friction head loss values and those calculated using Scobey equation, invalid for PVC pipe type, when combined with the typical Christiansen formula. This interesting finding led to improved results of Scobey equation through a developed Cs coefficient suitably valid for PVC pipe type via analytically mathematical derivation. And accordingly, the RMSD value dropped from about 8.6 to 1.6 m.
Water management in Saudi Arabia is facing major challenges due to the limited water resources an... more Water management in Saudi Arabia is facing major challenges due to the limited water resources and increasing uncertainties caused by climate change. This paper presents an analysis of the daily, monthly and annual mean, maximum and total rainfall records of the Saudi meteorological data for nineteen cities covering the all thirteen districts for more than three decades (1980 to 2010). An increased annual total and maximum rainfall was observed for 6 cities with the decreased trends in both parameters for the same number of cities. For the reaming seven cities, however, an increased annual maximum rainfall trend was seen in opposite to the decreased annual total rainfall. This opposite rainfall trend is also seen for the 12 months of the year for the same city which signifies the variability of changing climate pattern not only in different districts but also during the year. The increased rain intensities due to climate change results in flooding of short in urban centers which are designed based on dry climates. Finally, the recommendations are made for the rooftop rainwater harvesting and management to cope with the increasing short-duration floods and to provide an additional source of drinking water. Co-operations among official efforts, local NGOs and public are suggested for better results of water supply management due to rainwater harvesting in Saudi Arabia in a changing climate associated with increased rainfall intensities.
Water management in Saudi Arabia is facing major challenges due to the limited water resources an... more Water management in Saudi Arabia is facing major challenges due to the limited water resources and increasing uncertainties caused by climate change. This paper presents an analysis of the daily, monthly and annual mean, maximum and total rainfall records of the Saudi meteorological data for nineteen cities covering the all thirteen districts for more than three decades (1980 to 2010). An increased annual total and maximum rainfall was observed for 6 cities with the decreased trends in both parameters for the same number of cities. For the reaming seven cities, however, an increased annual maximum rainfall trend was seen in opposite to the decreased annual total rainfall. This opposite rainfall trend is also seen for the 12 months of the year for the same city which signifies the variability of changing climate pattern not only in different districts but also during the year. The increased rain intensities due to climate change results in flooding of short in urban centers which are designed based on dry climates. Finally, the recommendations are made for the rooftop rainwater harvesting and management to cope with the increasing short-duration floods and to provide an additional source of drinking water. Co-operations among official efforts, local NGOs and public are suggested for better results of water supply management due to rainwater harvesting in Saudi Arabia in a changing climate associated with increased rainfall intensities.
Proceedings of The 4th IWA-ASPIRE Conference & Exhibition, 2011
Water Management in Saudi Arabia is facing major challenges due to the limited water resources an... more Water Management in Saudi Arabia is facing major challenges due to the limited water resources and increasing uncertainties caused by climate change. This paper presents an analysis of the daily, monthly and annual mean, maximum and total rainfall records of the Saudi meteorological data for nineteen cities covering the all thirteen districts for more than three decades. An increased annual total and maximum rainfall was observed for six cities with the decreased trends in both parameters for the same number of cities. For the reaming seven cities, however, an increased annual maximum rainfall trend was seen in opposite to the decreased annual total rainfall. This signifies the variability of changing climate pattern not in different districts but also for the different cities of the same district. This trend also highlights the increased rain intensities which results floods of short durations causing more damage to the cities. Finally, these preliminary assessments of any systematic changes in the rainfall pattern over the period 1980–2010 are viewed to demonstrate the value of rainwater harvesting as a local adaptation to climate change for sustainability of water resources in this region.
Problem statement: Reference agro-climatic Weather Stations (WS) are rarely found in newly reclai... more Problem statement: Reference agro-climatic Weather Stations (WS) are rarely found in newly reclaimed areas. The usage of weather data from non-reference WS may lead to inaccurate estimations of Evapo Transpiration (ET), especially if the non-reference stations are distant from the reclaimed location. Approach: Weather data from four WS located at Riyadh were used to calculate ET by using Penman Monteith (PM) and Hargreaves equations. PM equation was applied with both alfalfa and grass reference crops. Calculations were done with and without temperature correction for non-reference weather stations. All calculations were compared with measured lysimeter data and corrections in Hargreaves formula were suggested. Results: (1): Weather data from non-reference WS can be used safely to calculate ET only when temperature corrections are applied. (2) Hargreaves formula underestimates ET at all locations in the study area. By applying the simple linear correction to the data, highly acceptable results are obtainned. (3) The ET ratio between alfalfa and grass in Riyadh is 1.25. Conclusion: The study concluded that temperature correction for non-reference WS is essential to ensure acceptable ET calculations. Usage of Hargreaves formula is recommended with the corrections suggested in the study due to its simplicity.
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 (ETref) 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 hc varies from 5 to 105 cm with increment of a centimetre. The developed models were spatially validated using climatic data from 1980 to2010 taken from another six meteorological stations. The results showed that the eight ETref models developed using the ANN technique were slightly more accurate than those developed using the GEP technique. The ANN models’ determination coefficients (R2) 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’ R2 values ranged from64.4% 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.
A soil box was used to investigate the water movement and soil water distribution around subsurfa... more A soil box was used to investigate the water movement and soil water distribution around subsurface drip laterals with two emitters in the presence of a thin layer of polyacrylamide (PAM). Sandy soil was uniformly packed into a soil box. The PAM was applied at a rate of 29.3 kg ha-1 as a 0.01% solution by spraying it directly onto the soil surface at the required depths. With an operating pressure of 150 kPa and no PAM layer, the water consumption with a dripper line depth of 0.15 m was 12% lower than with a dripper line depth of 0.10 m. The greatest improvement in soil water-holding capacity after the addition of a PAM layer (47%) was observed when the dripper line was placed at a depth of 0.15 m under an operating pressure of 100 kPa. With a dripper line depth of 0.15 m and an operating pressure of 100 kPa, the average moisture content in the vertical planes below and above the dripper line directly increased by about 7.4 and 20%, respectively, with PAM layers at 0.25 and 0.30 m depths when compared with the moisture content with no PAM layer. The combination of a dripper line depth of 0.15 m, a PAM layer depth of 0.30 m and an operating pressure of 100 kPa will achieve optimal water management.
Identifying the shortwave solar radiation, Rs, is very important in various fields of science whi... more Identifying the shortwave solar radiation, Rs, is very important in various fields of science which is calculated by mathematical models if not measured experimentally. These models depend on the coastality factor, kr. Several equations are developed to calculate kr but with errors of estimation. The aim of this paper was to develop a local formula to calculate kr from temperature range. Based on the 30-year climate data for 29 weather stations throughout the Kingdom of Saudi Arabia (KSA), monthly temperature ranges were calculated. The hyperbolic equation was derived based on the best-fit analysis and the resulted errors of four statistical parameters were compared with any other established formula. The average of the absolute percent error was estimated as 2.1% as compared with 6–11% of the various published models. Results show that kr is inversely proportional to the distance from the coast and the altitude. In addition, it was found that urbanization has a considerable effect on kr and the noncoastal but high-population cities behaved similar as coastal cities. It is recommended to use the proposed equation due to its accuracy for the KSA instead of using other models. More research is needed to further investigate the effects of urbanization on the kr.
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 R2 (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. OPEN ACCESS
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 ...
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Papers by Prof Alazba
stations. The Hargreaves (HRG) formula was used instead of the Penman-Monteith formula due to the ease of calculation of HRG formula, as it almost require only temperature. For each station, two formulas were derived considering both standard and non-standard AWS. Results show very good statistical representation of the formulas, with average root mean squared deviations of 0.73 and 0.57 and the mean percent errors of 1.22%, and 1.12% while considering the standard and non-standard AWS, respectively. Results also confirm the importance of temperature correction when using data from non-standard AWS, especially for the stations in the Middle to Midwest region (e.g. Arriadh,
AlQassim, and Almadina); where the errors of using non-standard AWS data may be up to +24% of the correct ETo value, which results in a massive waste of water.
OPEN ACCESS
stations. The Hargreaves (HRG) formula was used instead of the Penman-Monteith formula due to the ease of calculation of HRG formula, as it almost require only temperature. For each station, two formulas were derived considering both standard and non-standard AWS. Results show very good statistical representation of the formulas, with average root mean squared deviations of 0.73 and 0.57 and the mean percent errors of 1.22%, and 1.12% while considering the standard and non-standard AWS, respectively. Results also confirm the importance of temperature correction when using data from non-standard AWS, especially for the stations in the Middle to Midwest region (e.g. Arriadh,
AlQassim, and Almadina); where the errors of using non-standard AWS data may be up to +24% of the correct ETo value, which results in a massive waste of water.
OPEN ACCESS