Mohammad Valipour

Future of agricultural water management in Africa

This paper aims to estimate ratio of area equipped for irrigation to cultivated area (AI) in Africa in 2035 and 2060 using studies of agricultural water management from 1962 to 2011. For this purpose, all necessary information was gathered from Food and Agriculture Organization of the United Nations (FAO) and their values were checked using The World Bank Group (WBG). Among all presented data in the FAO database, 10 indices were selected (due to more importance and more availability for all the regions in Africa). The selected indices were analysed for all seven regions in the study area and the amount of AI was estimated by three different scenarios and using other nine indices. The results show that changes of AI are 0.3% to 49.5% and 16.5% to 83.2% from 2011 to 2035 and 2060, respectively. Indian Ocean Islands has a better potential to increase AI in the future. A considerable note is the change of irrigation status in the future than the current status. In 2011, AI of Sudano-Sahelian is more than AI of Indian Ocean Islands, however, in the future; AI of Sudano-Sahelian would be less than AI of Indian Ocean Islands based on all scenarios.

Simulation of open- and closed-end border irrigation systems using SIRMOD

In many regions in the world, more than 90% of areas equipped for irrigation apply surface methods. The major problem of the surface irrigation system is low performance due to poor design, operation, and maintenance. Use of the mathematical models for simulation of surface irrigation is necessary for reducing costs and decrease of time in analysis of indexes including application efficiency and distribution uniformity. This study aims to simulate border irrigation systems using the SIRMOD (surface irrigation simulation, evaluation and design, developed by Utah State University, Logan, UT, USA) software package under open- and closed-end conditions. For this purpose, 22 sets of data including four no-cultivated open-end borders, nine no-cultivated closed-end borders, and nine cultivated closed-end borders were used. The results showed that the models predicted open-end conditions better than closed-end for recession time. In addition, the hydrodynamic (HD) and the zero inertia (ZI) models estimated volume of infiltrated water, equal or less than volume of observed water in all the borders. Although the HD model uses the Saint-Venant equations without simplification, during numerical solution of them by the software, uncertainty is raised due to further calculations than the ZI and kinematic wave models. This leads to further error of the HD model than the other models in some cases.

Agricultural water management in the world during past half century

The present paper aims to estimate the areas equipped for irrigation and desirability of agricultural water management in the world. For this purpose, all necessary information was gathered from Food and Agriculture Organization and checked using World Bank Group. The selected 18 indices were analysed for all 26 regions in the area studied, and the extent of area equipped for irrigation to cultivated area was estimated by 2 different formulas and other 9 indices. In addition, an average index was calculated using various methods to assess region conditions for agricultural water management. The results show that Central Asia is the best region for agricultural water management and the value of relative error is less than 20%. The capability of irrigation and drainage systems was studied using other eight indices with more limited information. The results indicated that trial-and-error policies should be avoided and expert comments be applied to irrigation systems for any crop.

A comprehensive study on irrigation management in Asia and Oceania

The aim of this paper was to study the land use index (equipped area for irrigation per cultivated area, AI) and irrigation management in Asia and Oceania during past decades. For this purpose, all necessary information was collected from Food and Agriculture Organization of the United Nations (FAO). Among all presented data in the FAO database, 10 indices were selected. These indices were analysed for all 64 countries in Asia and Oceania, and the extent of AI was estimated by two different methods and other 9 indices. The results show that using all the 9 indices, the value of relative error will be less than 20%. Prioritization of the indices has shown that national rainfall index (NRI) and the difference between NRI and irrigation water requirement had a highlighted effect on the estimation of AI.

Application of new mass transfer formulae for computation of evapotranspiration

This study aims to compare mass transfer-based models to detect the best model under different weather conditions. For this purpose, weather data were gathered from 181 synoptic stations in 31 provinces of Iran. The reference crop evapotranspiration was estimated using 11 mass transfer-based models and was compared with the FAO Penman–Monteith model. The results showed that the Penman model estimates the reference crop evapotranspiration better than other models in the most provinces of Iran. However, the values of R2 were less than 0.90 for 24 provinces of Iran. Therefore, the models were calibrated using new formulae and preciseness of estimation was increased. The mass transfer-based models estimated the reference crop evapotranspiration in the eastern provinces (desert regions) of Iran better than other provinces. The best values of R2 were 0.96 and 1.00 for Trabert and Penman models in AR and TE, KE, and YA provinces before and after calibration, respectively.

Drainage, waterlogging, and salinity

Nowadays, various areas in the world have faced waterlogging and salinity problems, which are intensified by a myriad of factors including use of wastewaters for irrigation, unsuitable cropping pattern, torrential rains and floods, lack of sufficient drainage, uncontrolled drainage, lack of adequate knowledge, wrong management decisions, very poor construction and rehabilitation rates of drainage systems, increase of irrigation systems without paying any attention to their adverse impacts on soil and quality of water resources, etc. One effective way to reduce waterlogging and salinity problems is drainage. It is necessary to do a comprehensive study on previous works to arouse awareness of drainage, waterlogging, and salinity and to avoid trial and error policies in these fields. The present paper aims to study drainage, waterlogging, and salinity in the different regions of the world and to present challenges and prospects for further research and making a better decision in this field. The results indicate that the frequency distribution of studies carried out in India, Australia, the USA, Pakistan, and other countries is 23%, 20%, 15%, 12%, and 30%, respectively. While frequency distribution is 45%, 30%, and 25% for focus on salinity, comprehensive studies, and focus on waterlogging, respectively, based on the previous investigations.

Evaluation of radiation methods to study potential evapotranspiration of 31 provinces

The present study aims to calibrate radiation-based methods to determine the best method under different weather conditions. For this purpose, weather data was collected from different synoptic stations in all of provinces of Iran. The potential evapotranspiration was estimated using common radiation-based methods and a sensitive analysis was done for investigating variations of the methods. The results show that the Stephens method estimates the potential evapotranspiration better than other methods in the most provinces of Iran (10 provinces). However, the values of R2 were less than 0.98 for 15 provinces of Iran. The calibrated methods estimated the potential evapotranspiration in the south east of Iran better than other provinces. Precision of the methods calibrated has been increased in all provinces. The R2 values are less than 0.98 for only six provinces (WA, EA, GO, NK, AL, and QO). In the methods calibrated, the Abtew (for YA) estimated the potential evapotranspiration better than the other methods.

Study of different climatic conditions to assess the role of solar radiation in reference crop evapotranspiration equations

This study aims to assess radiation-based models versus the FAO Penman–Monteith (FPM) model to determine the best model using linear regression under different weather conditions. The reference evapotranspiration was estimated using 22 radiation-based methods and was compared with the FPM. The results showed that the Stephens method estimates the reference evapotranspiration better than other methods in the most provinces of Iran (nine provinces). However, the values of R2 were more than 0.9930 for 24 provinces of Iran. The radiation-based methods estimated the reference evapotranspiration near the Caspian Sea better than other regions. The most precise methods were the Berengena–Gavilan, Modified Priestley–Taylor, and Priestley–Taylor methods for the provinces ES (center of Iran), GI and GO (north of Iran) and the Stephens–Stewart method for IL (west of Iran). Finally, a list of the best performance of each method has been presented to use other regions and next research steps according to the values of mean, maximum, and minimum temperature, relative humidity, solar radiation, elevation, sunshine, and wind speed. The best weather conditions to use radiation-based equations are 23.6–24.6 MJ m−2 day−1, 12–20°C, 18–24°C, 5–13°C, and <180 hour month−1 for solar radiation, mean, maximum, and minimum temperature, and sunshine, respectively.

Comparative Evaluation of Radiation-Based Methods for Estimation of Potential Evapotranspiration

AbstractEvapotranspiration has a major role in agricultural and forest meteorology researches, hydrological cycle, irrigation scheduling, and water resources management. There are many methods to estimate the potential evapotranspiration including mass transfer, radiation, temperature, and pan evaporation-based methods. The present study aims to compare radiation-based methods to determine the best method under different weather conditions. The results discussed in this paper are from the data collected in the study area, but the method can be used in other similar regions. For this purpose, weather data was collected from 181 synoptic stations in 31 provinces of Iran. The potential evapotranspiration was estimated using 22 radiation-based methods and compared with the Food and Agriculture Organization of the United Nations (FAO) Penman-Monteith method. The results show that the Stephens method estimates the potential evapotranspiration better than other methods for provinces of Iran. However, the values ...

Future of the area equipped for irrigation

The aim of this paper is the estimation of area equipped for irrigation in the world in 2035 and 2060 using studies of agricultural water management during 1962 to 2011. Among all presented data in the Food and Agriculture Organization of the United Nations database, 10 indexes were selected (due to more importance and more availability for all the regions in the world). These indexes are permanent crops to cultivated area (PC, %), rural population to total population (RP, %), total economically active population in agriculture to total economically active population (LF (Agric), %), human development index (HDI), national rainfall index (NRI, mm year−1), value added to gross domestic product (GDP(Agric)) by agriculture (%), irrigation water requirement (IWR, mm year−1), percent of total cultivated area drained (D, %), difference between NRI and irrigation water requirement (mm year−1), and area equipped for irrigation to cultivated area (AI, %). These indexes were analyzed for all five regions in the study area and the amount of area equipped for irrigation to cultivated area (10th index) was estimated by three different scenarios and using the other nine indexes. The results show that changes of area equipped for irrigation are 12.1% to 70.7% and 29.0% to 99.9% from 2011 to 2035 and 2060, respectively.