Irrigation
M. Arjmand Sharif; H. Jafari
Abstract
Introduction: In hydrological studies, time series are observed as continuous or discrete. Groundwater level and rainfall can be considered as discrete time series. The most common way to measure the dependence between two variables in a discrete time series is to calculate the Pearson correlation coefficient ...
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Introduction: In hydrological studies, time series are observed as continuous or discrete. Groundwater level and rainfall can be considered as discrete time series. The most common way to measure the dependence between two variables in a discrete time series is to calculate the Pearson correlation coefficient (r). Pearson correlation test is a parametric test that quantitatively measures the linear relationship between variables. This coefficient is essentially a dimensionless index that describes the relationship between two variables numerically. The groundwater level is more or less influenced by rainfall, and this influence may be delayed for a variety of reasons. The process of comparing two time series in different time steps is called cross-correlation. In the cross-correlation analysis, the time-dependent relationship between the dependent and the independent variables is analyzed by computing the coefficients of cross-correlation for various time lags. Results are plotted on a graph called a cross-correlogram.Mashhad-Chenaran aquifer with an area of about 2527 km2 is the most important aquifer in Khorasan Razavi province. Unfortunately, so far in the Mashhad-Chenaran aquifer, the recharge lag time has not been calculated due to the very complex geological and hydrogeological conditions of the aquifer. In this study, an attempt has been made to calculate the groundwater recharge lag time.Materials and Methods: In this study, 15 years (Sep. 2001 to Sep. 2016) data of monthly depth to water-table and rainfall have been used . There is 74 active observation well in Mashhad-Chenaran aquifer. Out of 74 wells, 31 well were selected based on geological and hydrogeological conditions. To calculate the rainfall at the observation wells, the daily rainfall data from rain gauge and evaporation stations (25 rain gauge stations and 9 evaporator stations) have been used. First, the cumulative daily rainfall at each station for one month (from 15 months to 15 months later) was calculated. Then, a monthly rainfall raster was prepared using ArcGIS.Finally, the rainfall at the observation well was extracted from the raster file.Results and Discussion: The correlation coefficient between the groundwater level and rainfall was calculated for the 31 wells at two confidence levels (α = 0.05 and α = 0.1). The lag time was calculated based on the highest correlation coefficient for the two confidence levels. Results showed that the cross-correlation coefficient varied from at least 0.129 in the Tanglshour-Morgh Pardak observation well (very weak) to 0.495 in the Kalateh Sheikhha observation well (moderate). The coefficients of cross-correlation for various time lags were plotted on the cross-correlogram. In cross-correlogram, the month zero was equivalent to October and the month 11 was equivalent to September of the next year. It was observed that the trend of correlation coefficient followed the two specific patterns. In the first group, the water table usually reacts to rainfall after the second month. Then, the correlation coefficient gradually increased. The correlation coefficient reached its maximum in the fourth and fifth months and then decreased with a gentle slope. From the seventh month to the eleventh month the correlation coefficient has become negative. Although there was a significant relationship during these months, there was no cause-and-effect relationship between changes in the water table and rainfall. In the second group, the relationship between the groundwater level and rainfall was not significant at the 95% confidence level. This group includes Doghai observation wells, Qarachah, Shurcheh, Mochenan, Yekehlengeh, Chamgard, Ghahghahe, Tangleshour - Morgh Pardak, and Shorcheh. Changes in the correlation coefficient of these wells were very irregular and the relationship between rainfall and water table changes was probably influenced by other factors. The map of lag time showed that the spatial variations of the lag time completely followed the pattern of the Iso-depth map. In general, the lag time was a function of the depth to the water-table in the Mashhad-Chenaran aquifer. With increasing water depth, the lag time also increased. A closer look at the map showed that in the northern and southern margins of the first hydrogeological unit, the lag time was more than its center. In the northern and southern hydrogeological units, the lag time showed the greatest compliance with the groundwater depth. The amount of lag time from the northern margin of the aquifer to the south gradually increased and finally reached its maximum value in the Akhlamad, Torqabeh-Shandiz.Conclusion: As discussed previously, the groundwater level was influenced by rainfall, and this influence may be delayed for a variety of reasons. In this study, the groundwater response to rainfall has been estimated from 31 observation wells by cross-correlation method in a period of 15 years (Sep. 2001 to Sep. 2016). The correlation test results showed that after about 2 to 3 months, the effect of rainfall was gradually observed on the groundwater level and the correlation coefficient at the confidence level α = 0.05 and α = 0.1 for 77 % and 97% of wells became meaningful, respectively. The minimum lag time was 2 months and the maximum was 7 months. In general, the estimated lag time was well matched to the groundwater depth and fully followed the Iso-depth map pattern. The amount of groundwater recharge throughout the Mashhad-Chenaran aquifer was mainly controlled by the unsaturated area properties such as thickness, material, etc. Changes in groundwater depth were the major factor affecting the lag time. It seems that with the start of rainfall in late October, groundwater recharge in most wells begin in mid-autumn and continues until late spring. Most of the groundwater recharge takes place in late winter. In summer, rainfall has a very small role in groundwater recharge. In this period, the uncontrolled extraction of water from the aquifer and consequently a sharp and continuous drop in groundwater level plays a major role in water table fluctuations.
Z. Pashazadeh Laleh; H. Jafari; A.R. Vaezi Hir
Abstract
Introduction: The water is the major key in sustainable development, so it is necessary to be managed and conserved. The quality of surface water resources is mainly controlled by natural or geogenic factors including chemistry of recharge water, soil and geology processes, as well as the man-made contaminant. ...
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Introduction: The water is the major key in sustainable development, so it is necessary to be managed and conserved. The quality of surface water resources is mainly controlled by natural or geogenic factors including chemistry of recharge water, soil and geology processes, as well as the man-made contaminant. Qualitative indicators are used as effective managing tools in decision making programs. Water quality indices (WQI) are the simple and suitable tools to determine the quality statue of the water. In order to calculate the water quality index, many parameters are integrated in mathematical formula to represent the quality condition of the water with a number which classifies the quality in the scales of the weak to excellent. Many water quality indices were introduced by researchers and organizations around the world. Aji-Chay, one of the most important flowing rivers in East-Azerbaijan province, northwest of Iran, is passing through Tabriz plain in its way and finally ends to the Uremia lake. Regarding the focused industrial zones, agricultural field and urban areas in this plain, the river is highly vulnerable to pollution and quality degradation. So, this study was aimed to assess the Aji-chay River based on quality indicators, in order to helps its better management. Materials and Methods: In this research for assessing pollution of the Aji-Chay river using water quality indices, 16 sampling stations were located along the river and water samples were collected during wet (May 2016) and dry (September 2016) seasons. Electrical conductivity (EC), temperature, dissolved oxygen (DO) and pH were measured in the field and total dissolved solids (TDS), turbidity, major ions (Ca, Mg, Na, K, HCO3, Cl, SO4), nitrate (NO3), phosphate (PO4), biological oxygen demand (BOD), chemical oxygen demand (COD) and biological contaminants (fecal coliform) were determined in the laboratory. Quality indicators including the US national sanitary foundation water quality indices in the two forms of multiplicative (NSFWQIm) and additive (NSFWQIa) and Iranian surface water quality index (IRWQIsc) were used to assess the quality of the Aji-Chay river. Results and Discussion: Turbidity and Electrical conductivity (EC) is high at the upstream which is related to movement of the River in upper red formation (Miocene series) which enhances the chloride, sodium, calcium and sulfate. Arsenic concentrations are exceeding the drinking standards (0.01 ppm) across all samples mainly from a geogenic sources as well as discharge of wastewater in some areas. The elements Cd, Mn, Ni, Pb, Mo, Co, Zn, Fe and Al are mainly geogenic, whereas Cu, Ba and Cr are mostly originated from anthropogenic activities. Based on the results, river quality at the wet season is highly controlled by the main branch and Gomnab-Chay, but Mehran-rood plays the major role in downstream water quality at the dry season due to its higher discharge rate. The process was confirmed by Piper and Schoeller diagrams. Most of the parameters are increased in middle parts at the river where the concentrated sources of contaminates and discharge of wastewater increased the organic and biological constituents and nutrients especially in dry season. Assessing the river quality for agricultural uses based on modified Wilcox diagram shows except for Mehran-rood, the other samples are unsuitable for agriculture and the dry season quality is better than the wet season. Based on the results, increase in most parameters and so, pollution and quality degradation of the river are observed to the downstream. Assessing quality of the Aji-Chay river using US national sanitary foundation water quality indices in the two forms of multiplicative (NSFWQIm) and additive (NSFWQIa) and Iranian surface water quality index (IRWQIsc) confirmed the bad to very bad qualitative statue of the river in most stations especially in the middle parts of the Tabriz plain. The results revealed that quality degradation of Aji-Chay river is probably due to discharge of contaminants from municipal and industrial wastewaters (effluents), highlighting the need for managing actions to improve quality of this important river. Comparing the quality indices showed the priority of NSFWQIm (multiplicative form of US national sanitary foundation water quality indices) in quality classification and pollution assessment of the Aji-Chay river. Conclusion: Quality degradation of Aji-Chay river is probably due to discharge of contaminants from municipal and industrial wastewater effluents, indicating the need for managing actions to improve quality of this river. In this study priority of NSFWQIm (multiplicative form of US national sanitary foundation water quality indices) in quality classification and pollution assessment of the Aji-Chay river was confirmed.
Ziba Arabi Javanmard; Hadi Jafari
Abstract
Introduction: Recharge estimation is one of the major issues in management of groundwater resources. Many methods have been applied to calculate the groundwater recharge, among which the water table fluctuation, chloride mass balance and water balance methods have been widely used. In this study the ...
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Introduction: Recharge estimation is one of the major issues in management of groundwater resources. Many methods have been applied to calculate the groundwater recharge, among which the water table fluctuation, chloride mass balance and water balance methods have been widely used. In this study the recharge quantity into alluvial unconfined aquifer of Aleshtar in Lorestan province with an area of about 128 km2 was estimated using three methods of water table fluctuation, chloride mass balance and water balance. The aquifer is more important, as it supplies the water for agricultural consumptions. The aquifer is discharged by 322 pumping wells. It is also drained by the gaining river of Aleshtar which crosses the plain in a general trend of the north to the south.
Materials and Methods: Three methods of water table fluctuation (WTF), chloride mass balance (CMB) and water balance were used to calculate the recharge to Aleshtar aquifer in Lorestan province.
In water table fluctuation (WTF) method, water table data from 18 piezometers installed in Aleshtar aquifer during an 11-year period (2003-2014) were collected and analyzed. The values of groundwater rise () which is equal to the difference between the peak of the rise and low point of the extrapolated antecedent recession curve at the time of the peak were calculated and then multiplied by the specific yield to determine the value of recharge based on the following equation:
Δh/Δt (1)
In which R is recharge, Sy is the specific yield and Δt stands for the time.
Recharge value was also calculated by chloride mass balance (CMB) method. In this regard chloride concentrations were measured in 33 groundwater samples and 5 rainfall samples and then recharge was calculated by the following equation:
(2)
Where R is annual groundwater recharge (mm), P is annual precipitation (mm), is mean chloride concentration in rainfall (mg/l) and is average chloride concentration of groundwater (mg/l).
Recharge estimates were also performed by the water balance method based on the following equation:
(3)
In which R denotes groundwater recharge, is groundwater outflow, is groundwater inflow, is groundwater drainage, is evapotranspiration from the groundwater table, is groundwater pumping and is change in groundwater volume storage.
Results and Discussion: Investigating 11-year groundwater hydrograph of Aleshtar aquifer shows a decreasing trend against time. In the current situation, the annual rate of water table decline is about one meter. In order to estimate recharge value using water-table fluctuation method, the value of 0.05 was considered for specific yield based on dominant soil texture in drilling logs and the value of annual recharge into the aquifer was estimated at 28.3 million cubic meters. Temporal variations of recharge showed an increasing trend with time. This is probably related to capacity increase of the aquifer to receive recharging water due to the decline in water table. It was further confirmed by investigating the upstream and downstream hydrographs of the Aleshtar River which showed a decreasing trend in contribution of the groundwater (base flow) at the river discharge with the time. The average concentration of chloride ion in groundwater and rainfall samples were measured as 40.23 and 6.4 mg/l, respectively. Then, recharge value was calculated about 10 million cubic meters using chloride mass balance method. The annual water balance of the Aleshtar aquifer was investigated considering the main components of groundwater inflows (32.46 million cubic meters), groundwater outflows (6.25 million cubic meters), groundwater drainage by the Aleshtar river (15.76 million cubic meters), discharge by pumping wells (49.22 million cubic meters) and change in aquifer storage (-6.41 million cubic meters). The evapotranspiration was not considered as the depth to water table is more than 5 meters, anywhere. Then, the amount of annual recharge using water balance method was estimated about 32.4 million cubic meters.
Conclusion: The similarity of the recharge values calculated by water table fluctuation and water balance methods confirm the accuracy of the calculated total recharge by the both rainfall and irrigation return flows to the Aleshtar aquifer. By subtracting the irrigation return flows, the annual rainfall recharge is estimated at 18.5 and 22.6 million cubic meters by the water table fluctuation and water balance methods, respectively. Due to the uncertainties in recharge estimation by different methods, rainfall recharge to the aquifer was determined in the range of 10 to 22 million cubic meters per year and the rainfall recharge coefficient of 28% was introduced for Aleshtar aquifer.
H. Emami Heidari; H. Jafari; Gh. Karami
Abstract
Management of agricultural practices plays a vital role in reducing the use of limited water resources in arid and semi-arid regions which could result in their sustainability. In this research, the role of managing agriculture in sustaining flow of Zayandeh-rud was studied by calculation of rice water ...
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Management of agricultural practices plays a vital role in reducing the use of limited water resources in arid and semi-arid regions which could result in their sustainability. In this research, the role of managing agriculture in sustaining flow of Zayandeh-rud was studied by calculation of rice water requirement (actual evapotranspiration) in paddy fields of Zarrin-shahr by using method of FAO-56 and comparing the results assuming a shift in cropping pattern from rice to other crops. Rice water requirement was estimated at 1485 mm and the volume of water required for irrigation of paddy fields with area of about 6630 Hectare was estimated at 77 MCM. Volume of irrigated waterwas also evaluated by water balance method, confirmed the reliability of FAO-56 method. The results show that, replacing rice or wheat-rice cropping pattern with some possible crops such as bean, maize, walnut, apple and grape decreases irrigation requirements about 27, 15, 24, 29 and 40 MCM, respectively. Generalizing results for the total paddy fields in Isfahan Province with estimated area of about 20000 Hectare will result in an increase of about 3.4 to 9.1 m3/s in Zayandeh-rud discharge during critical months of June to October, when the river flow highly decreases, causing sustainable flow of the river through the year.