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Showing 10 results for Water Table

Kh. Bargahi, S. A. A. Moosavi,
Volume 10, Issue 3 (10-2006)
Abstract

Limitation of suitable water resources is the most important problem of agriculture in Iran. Considering the condition of shallow and saline groundwater in many parts of Iran, and relative resistance of safflower to salinity, it is necessary to study the contribution of groundwater to water consumption of safflower. In this research, the effects of different water table depths and salinity of groundwater on contribution of groundwater to evapotranspiration of safflower were studied. The treatments were four levels of water table depth (50, 70, 90, and 120 cm), two levels of groundwater salinity (EC of 0.6, and 10 dSm-1 ), and two irrigation regimes (irrigation with a depth of water equal to 75 percent of evaporation from water surface and frequency of 5 days, and no irrigation). The experiment was performed in a randomized complete block design with treatment combinations arranged in factorial manner and three replications. For fixing the water table in the pots (PVC pipe 200 mm in diameter and 120 cm high), a special equipment was built on the principle of Marriot bottle that was able to measure the contribution of groundwater to evapotranspiration of the plants. Results showed that salinity of groundwater, irrigation regime, and their interactions have significant effects on evapotranspiration of safflower. In addition, effects of water table depth, salinity of groundwater, irrigation regime, interaction of salinity and water table depth, interaction of water table depth and irrigation regime, and interaction of water table depth, salinity, and irrigation regime on evaporation from soil surface were significant. The ratio of contribution of groundwater to plant water consumption and evapotranspiration was in the range of 52.5 and 54.9% for saline groundwater and 81.7 to 82.7% for fresh groundwater. The ratio of evaporation from soil surface and evapotranspiration was in the range of 4.5 to 53.6% for different treatments. In all treatments of groundwater depths, irrigation treatment significantly decreased evapotranspiration, but no significant change in evapotranspiration was observed in irrigated and no irrigated treatments. Maximum amount of evapotranspiration (251 cm) occurred in the 50 cm depth of groundwater with salinity of 0.6 dS/m under irrigated condition, and minimum amount (43.9 cm) occurred in the 90 cm depth to groundwater with salinity of 10 dS/m under no irrigation condition. Generally, salinity of groundwater caused significant decrease in evapotranspiration, evaporation from soil surface, transpiration, and contribution of groundwater to evapotranspiration.
S. Azizpour, P. Fathi, K. Nobakht-Vakili,
Volume 16, Issue 60 (7-2012)
Abstract

Soil saturated hydraulic conductivity (k) and effective porosity (f) are the most important parameters to simulate the processes associated with irrigation, drainage, hydrology, leaching and other agricultural and hydrological processes. Present methods to measure these parameters are often difficult, time consuming and costly. Therefore, a method which provides more accurate estimates of these parameters is essential and is considered inevitable. The purpose of this study was simultaneous estimation of k and f using approach inverse problem. In this study, analytical drainage model of Glover-Dam was used to simulate the inverse problem method. Also, genetic algorithm was used as an optimization technique for determination of optimal values of k and f. In order to measure the data required for calibration and evaluation of the proposed inverse problem model, a physical model was designed and constructed in the laboratory. The results showed that the proposed method is good for simultaneosly estimating simultaneous soil k and f. Also with variable f assumption, the prediction error of water table around the drainage was reduced significantly.
S. M. Mousavi, A. Hoshmand, S. Bromandnasab, M. Yazdani,
Volume 16, Issue 60 (7-2012)
Abstract

The common method of irrigating rice in paddy fields of Iran, like most countries, is flooded irrigation. The water required in this method is too much. However, because of water shortage in recent years, and malfunctioning of irrigation systems, it is needed to use water in a reasonable way and increase water use efficiency. Therefore, it is necessary to know water loss amounts at the paddy fields. The deep percolation (DP) was measured by closed- and open-bottom rings in 4 locations, and 7 sites at each location, of paddy fields in Somae-Sara city, Guilan province. These locations were selected on the base of different physiographic units. The average DP of these locations was also monitored during plant growth season. The measurements were performed twice a week. Results showed that the rate of DP varied during the season, and could take a positive or negative value. The most important factors of these variations were the lateral seepage (from surrounding rice fields) and the high perched groundwater table in paddy fields.
M. Akbari, B. Nazari, M. Parsinezhad , H. Ebrahimian,
Volume 16, Issue 62 (3-2013)
Abstract

This study was conducted on subsurface drainage network under operation in Behshahr. DRAINMOD model was used to simulate drainage system using measured data in 2006. The model was evaluated to estimate soil hydraulic conductivity by comparing the measured and predicted values of water table depth and drain discharge for different values of hydraulic conductivity. The results of this method were compared with the results of output drainage water method (as a baseline method). Use of water table depth simulation results in estimating hydraulic conductivity model resulted in considerable error, while the simulation results of drain discharge rate could be used with good accuracy for estimating it. There was a small difference between the output drainage water method and the inverse solution of DRAINMOD model to estimate soil hydraulic conductivity (2.3 and 2.5 cm/h, respectively). Thus, the comparison between the measured and predicted values of drain discharge could be a good criterion to estimate soil hydraulic conductivity using the inverse solution of the DRAINMOD model
Mohammad Hossein Noori Gheidari,
Volume 17, Issue 64 (9-2013)
Abstract

In order to monitor the changing water table in the field, determination of the main sampling points is very important to reduce sites and save time and cost. Principal Component Analysis (PCA) is one of the data reduction techniques used to extract the important components that explain the variance of a system. In this paper, the PCA was used to identify the effective wells of Qheidar Aqufer, Zanjan, to determine the groundwater level and remove the less important ones. From the study region which an area of about 920 km2, 48 wells (sites) were investigated. Using PCA, the relative importance of each well was calculated between 0 (for completely ineffective well) to 1 (for the very effective wells). The study showed the elimination of wells whose relative importance was less than 0.5 (i.e. half the total number of wells), coefficient of variation of groundwater level relative to the use of all wells did not greatly increase, and the error to determine the level of groundwater was less than 13 percent.
Seyyed S. M. A. Maddahzadeh., K, Esmaili, B. Ghahraman,
Volume 21, Issue 1 (6-2017)
Abstract

Bi-level drainage system is a type of underground drainage systems, in which adjacent drainage lines are installed at different depths. In the Hydraulics Laboratory, Ferdowsi University of Mashhad, a model was built, that include a cube tank 2 meters in length, width and height of 1 meters was made ​​of galvanized. In this model, two rows 20 cm apart from each other drains were installed. As drainage, a pipe of three layers to the outer diameter of 16 mm was made of PVC. Within this model of stratified soil was used as a soil layer of low permeability with a hydraulic conductivity of 1.15 cm per hour, thickness of 20 cm soil layer between two light soil layer with 30-cm thickness for bottom layer and 20 cm for the top layer with a hydraulic conductivity of 1.55 cm per hour. For accurate measurement of the water table Behavior in the soil at each point of the model, some piezometer distance of 10 cm from each other on the floor model was installed. After Outfit of model with blow-off valve, Experiments with a heavy irrigation for different intervals between depths of 30 and 50 cm were used in drainage and water table elevation values ​​as observed values ​​were extracted from the model. The results show that the values ​​obtained from Upadhyaya and Chauhan Equation only in small area of water table profiles, which include an area of between the two drainage, are consistent with observed and with a wider distance between deep and shallow drainage, time of drop in water table increased.


M. Khoshravesh, M. Valizadeh,
Volume 21, Issue 2 (8-2017)
Abstract

Construction of a dam in the upstream of Tajan basin, as one of the human activities in order to provide drinking water, hydropower, agriculture, flood control or other purposes, can be effective on other sectors such as water resources. The purpose of this study is investigating the impact of Rajaei dam on groundwater resources in Sari-Neka plain during 26 years period (1985-2011) using geostatistical method, parametric and non-parametric tests. The results of statistical tests showed that groundwater table variation during 26 years has experienced insignificant upward trend. Quality factors such as EC, TDS, TH, Cl, SO4, Mg, Na and SAR had significant downward trend at 5% confidence level for Pearson and Kendall test. The Quality changes of groundwater resources in the region had good condition due to construction of dam. The results of spatial analysis for the study area using Kriging interpolation method in the three years for 1985, 1999, 2011 showed that in 1999 (the year of exploitation of the dam) most of the quality factors had reached the highest level from 1985 until the dam operation (1999) and then decreased to 2011. The results of this study showed that, agricultural activities after dam construction, operation of irrigation system and drainage network design of Rajaei dams, have raised the water table in northern part of the region and consequently had a significant impact on the quality of water resources.
 


M. Noshadi, S. Karimi,
Volume 22, Issue 3 (11-2018)
Abstract

The growth of world population and the demand for agricultural products can be regarded as one of the important issues that humanity has ever faced. There are serious concerns regarding surface and ground water pollution by nitrates because of using nitrogen fertilizers in the agriculture. Improving agricultural water management systems can reduce nitrate in drainage outflow and therefore, reduce the environmental pollution. This research was conducted to evaluate the effect of the controlled drainage and nitrogen fertilizer on nitrate leaching and environment pollution as a factorial randomized complete block design in Shiraz College of Agriculture. The treatments consisted of three fertilizer levels; 0, 200 and 300 kgN/ha, and three water table depths: free drainage, control water table at 60cm (CD60) and 90 cm (CD90) depths, respectively. According to the results, the value of drainage water and nitrate losses in the controlled drainage toward free drainage were significantly increased. The mean reduction of drainage water in CD60 and CD90, as compared to free drainage, was 59.3 and 35.7%, respectively. The decrease nitrate losses, as compared to free drainage, was 72 and 44%, respectively. The total value of nitrate leaching in 200 and 300 kgN/ha fertilizer treatments was 1.86 and 2.48 times of 0 kgN/ ha.

M. M. Matinzadeh, J. Abedi Koupai, A. Sadeghi-Lari, H. Nozari, M. Shayannejad,
Volume 23, Issue 3 (12-2019)
Abstract

Selection of drainage equation with acceptable accuracy has always been a challenge for designers to design subsurface drainage systems. In this research, seven steady state drainage equations were used for predicting daily and cumulative drainage rate on a farmland of sugarcane in Imam agro-industrial Company. These drainage equation included Hooghoudt, Ernst, Kirkham and Dagan that have been developed in the past and Mishra and Singh, Henine and Yousfi et al that recently developed. The statistical indices consist of P-value, RMSE, R2 and Percentage Error of estimating cumulative drainage rate were calculated for Hooghoudt equation 0.9501, 1.49 (mm/day), 0.80 and -0.19%, respectively. For Ernst equation 0.0001, 2.46 (mm/day), 0.34 and 16.98%, respectively. The result of performance of drainage equations revealed that Hooghoudt and Ernst equation were as the equations with the highest and lowest accuracy in predicting drainage rate, respectively. Also from the newly developed equations, the Yousfi et al equation was found with relatively well accuracy to predict the drainage rate. This equation was placed in second rank after Hooghoudt equation and other equations showed poor performance. Thus, with selection of the appropriate drainage rate, the Hooghoudt equation is suggested for designing of drain spacing in medium to heavy textured soils such as sugarcane agro-industrial.

T. Mohammadi, V. Sheikh, A. Zare, M. Salarijazi,
Volume 27, Issue 3 (12-2023)
Abstract

A quantitative study of groundwater resources and accurate monitoring of changes over time, especially in areas facing limited water resources, is considered essential for proper management and sustainable exploitation of these resources. Golestan province, one of the semi-arid provinces of Iran has faced a drop in the groundwater level and an increase in the salinity of the groundwater due to the excessive withdrawals from the groundwater table and the reduction of atmospheric precipitation in the past few years. Gorgan Plain with an area of about 4727 square kilometers is one of the largest plains in Iran and the most important plain of Golestan province in terms of water supply for agricultural and drinking purposes. In this plain, there is a network of piezometers and observation wells that include continuous monthly measurements for more than 30 years. The objective of this research was to investigate the changes in the groundwater level of shallow (30 years (1989-2018)) and deep (22 years (1997-2018)) wells. The Man-Kendall method was used to reveal the trend and Pettitt, Normal Standard, and Buishand methods were used to identify sudden change points in a time series of groundwater levels in 49 shallow wells and 12 deep wells. The results of this research showed that the groundwater level in most of the studied wells had a significantly decreasing trend at a significant level of 5%. Also, the largest amount of groundwater loss was in the southern and southwestern parts of the plain, which can be attributed to a large amount of water taken from the wells due to their proximity to urban areas and some local conditions such as the proximity of the wells of this area are located in altitudes and at the entrance border of the aquifer. In the same way, as it rises, the fall decreases in the middle of the plain, and the amount of fall decreases in the northern areas and the edge of the Caspian Sea. It can be related to the proximity to the Caspian Sea and the high water table, and as a result, the inappropriate quality of water and land (high salinity and low fertility), which has caused the water withdrawal from this area to be less.


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