The purpose of this study is to evaluate the QUALITY of the Hablehroud river in Semnan based on the Iran WATER QUALITY Index for SURFACE WATER RESOURCES-Conventional Parameters (IRWQISC). Eleven parameters of COD, BOD5, dissolved oxygen, electrical conductivity, Fecal coliform, ammonium, nitrate, phosphate, turbidity, total hardness, and pH were monitored during four seasons from winter 2020 to autumn 2020 in three sampling stations; upstream of Bonkooh village (A), downstream of the village (B) and Deh Sarab (C). The highest value of IRWQISC was 55. 6 in Station A in summer and the lowest value was 40. 4 in Station B in winter. The WATER QUALITY of the river in Station A in summer was therefore better than the other stations and other seasons. To investigate the effect of each parameter on the WATER QUALITY index and also to investigate the interaction of the above-mentioned parameters, the experiment was designed in the three studied stations in summer by using the Design Expert software. First, the parameters that had a greater effect on the IRWQISC value were screened by the Plackett-Burman method and then the RSMBBD method was used to analyze the data. The parameters of EC, phosphate, nitrate, turbidity, and pH had the largest contribution in the IRWQISC with respective values of 51. 61%, 23. 13%, 14. 44%, 3. 17%, and 2. 38%. The coefficient of determination (R2) using the BBD method was 0. 9982 which indicates that the model is valid.

Drought is a phenomenon that threating WATER QUALITY in addition to its shortage. In this paper we investigate the effect of drought on SURFACE WATER QUALITY of Kashkan WATERshed. For this purpose, during the collection of meteorological data and WATER QUALITY data during 20 years (1987 to 2009) from Meteorology and WATER RESOURCES offices of Lorestan province, initially duration and severity of meteorological and hydrological droughts were determined by SPI, RDI and SDI Indices. Later in periods that intensity and duration of drought were more than other period, percent changes of WATER QUALITY to the long-term average was calculated then agricultural and drinking WATER QUALITY analysis in the form of two charts Schuler and Wilcox was performed. Also, the linear trend of data was investigated for highlighting the effect of drought on WATER QUALITY changes. Results indicate that drought has significant changes in parameters of SURFACE WATER RESOURCES especially EC, TDS, NA, CL and SO24.Also the results showed that WATER QUALITY in terms of Schuler & Wilcox graphs has changed in effect of drought. The QUALITY of Afarineh and Chan Anjir rivers drinking WATER has changed from ok classes to acceptable grade and for agricultural purposes has changed from C2S1 grade to C3S1 grade. Finally, the overall analysis of linier trend graphs shows that the increasing trend of drought has a negative impact on SURFACE WATERs QUALITY of Kashkan WATERshed.

Introduction The WATER quantity and QUALITY has always been one of the main challenges in the issue of allocating WATER RESOURCES for different uses. WATER QUALITY management requires the collection and analysis of large amounts of WATER QUALITY parameters that will be evaluated and concluded. Many tools have been found to simplify the evaluation of WATER QUALITY data, and the WATER QUALITY index (WQI) is one of these widely used tools. In summary, the WQI can be defined as a number obtained from the combination of several QUALITY parameters based on standards for its extraction. The aim of this study was to develop and introduce the new SURFACE WATER Drinking WATER QUALITY Index (SDWQI) adopt the WATER QUALITY parameters measured on hydrometric stations of Iran. In developing this index, criteria such as the availability of required parameters in most rivers and simple and accurate methods have been considered. Also, the ability to calculate with the minimum general parameters of WATER QUALITY, simple calculations and in terms of the international standard WHO for drinking is one of the advantages of the introduced index. Materials and Methods For this purpose, 12 WATER QUALITY parameters including Total Dissolved Solids (TDS), Electrical Conductivity (EC), Total Hardness (TH), pH, Chloride (Cl-), Sulfate (SO42-), Carbonate (CO32-), Bicarbonate (HCO3-), Magnesium (Mg2+), Sodium (Na+), Calcium (Ca2+) and Potassium (K+) have been used from Rudbar and Astaneh hydrometric stations located on Sefidroud river. Then initial preprocessing on data e. g. correlation analysis, and multivariate statistical methods including cluster analysis (CA) and principal components analysis (PCA) are used to selecting and weighting of WATER QUALITY parameters using the “, clustering”,and “, factoextra”,packages in R 4. 1. 1. In order to develop the SDWQI were performed four steps including, parameter selection, sub-indexing, weighting and aggregation of the index. Also, in order to evaluate the index of the present research, the results of the SDWQI have been compared with the WHO drinking WATER QUALITY index and Schoeller drinking WATER QUALITY classification. Results and Discussion Correlation analysis between WATER QUALITY parameters shows a significant correlation between TDS, EC and TH parameters and also with Cl-, Ca2+ and Mg2+ parameters at the level of 1% in both Astaneh and Rudbar stations. On the other hand, the lowest values of Pearson correlation coefficient are related to pH and CO32-parameters with other QUALITY parameters. The results of CA indicate that most of the WATER QUALITY parameters are located in separate clusters. So only the parameters TDS, EC, Cl-and Na+ in both Rudbar and Astaneh stations are in the same cluster. The weights of the parameters showed that TDS and K+ are assigned with the highest and lowest weights equal to 0. 163 and 0. 031 based on PCA method. Also, PCA results show that first and second principal components covered 59. 3% and 67. 6% of the total variance of measured WATER QUALITY parameters in Rudbar and Astaneh stations, respectively. WATER QUALITY classification results indicate that (40. 5%, 16. 4% and 23. 7%) and (90. 1%, 73. 1% and 57. 3%) of data in Rudbar and Astaneh stations, respectively, fell into the excellent and good categories for drinking purposes based on Schoeller classification, WHOWQI and SDWQI. Conclusion Generally, the comparison of the SDWQI with the WHO index and the Schoeller classification shows the rigidity of the new index in the classification of WATER QUALITY for drinking purposes. Each WATER QUALITY index developed in order to evaluate the uncertainty of results, should be tested for data with different characteristics in terms of the range of variation with different limit values​, ​,(minimum and maximum). The index developed in the present study is no exception to this rule and in order to better evaluate the results, it is suggested that to be evaluated and analyzed with data from other hydrometric stations. Another important points that should be considered in using any WATER QUALITY index, including the present research index, is to examine the allowable limits of WATER QUALITY parameters that are not considered in these indicators. The results of the study indicated that, two most important steps in the development of a QUALITY index that have a great impact on its results are sub-indexing and weighting of parameters. According to the results, two ideas recommended for future research. One, choosing an appropriate method such as non-deterministic (fuzzy) and intelligent (machine learning) methods to sub-index the parameters and two, to weigh the parameters more effectively, multivariate statistical methods such as clustering, factor analysis and principal component analysis should be used.

In recent years, the improper increase of agricultural activities along riverbanks and discharge of household, agricultural, and industrial wasteWATER into them has led to a significant reduction in the QUALITY of SURFACE WATER. Polluted or contaminated WATER sources can have a negative impact on the entire life cycle. In this study, the trend of changes in the WATER QUALITY of Neka River, from its source to its connection to the Caspian Sea, has been investigated. Samples were collected at three different points along the river during different seasons in 2021 and were analyzed using IRWQIsc and NSFWQI standards. Results showed that, based on the IRWQIsc index, the river is relatively good QUALITY, and according to the NSFWQI index, it is of moderate QUALITY, but at station 3, the river's QUALITY is relatively poor using both indexes. The overall WATER QUALITY follows a downward trend from the source to the outlet, with greater declines in QUALITY during warmer seasons due to increased agricultural activities in the river basin, with the largest decrease in QUALITY observed in spring and the smallest decrease in QUALITY in the colder seasons, especially in winter.

The increasing demand for WATER, especially in semiarid regions, poses new challenges for WATER RESOURCES managers. Hence, they must understand the interactions between SURFACE WATER and groundWATER systems, especially under uncertainty. In groundWATER systems, uncertainty arises from boundary conditions and aquifer parameters, while in SURFACE WATER systems, uncertainty stems from the natural variability of the climatic inputs such as precipitation, air temperature, and river flows and, to a lesser degree, from SURFACE model parameters. The main objective of this paper is to present a simulation model for examining the interaction(s) between SURFACE WATER and groundWATER under geologic uncertainty. This model was specifically developed for the study of the Najafabad semiarid plain in Iran. The plain aquifer under study is recharged by lateral groundWATER flow from boundaries, irrigation percolation, canals and river seepage, and precipitation directly on the plain. GroundWATER flow and groundWATER/SURFACE-WATER interactions were simulated for steady and transient flow conditions using MODFLOW-2000 for average monthly stress conditions in the system during 2001-2004. Calibration of the model was performed by comparing simulated and observed heads, and observation measurements made on a monthly basis during 2002-2004 in 49 observation wells. The Monte Carlo method was used for uncertainty analysis and the investigation of how different model structure alternatives would affect the estimated parameter values. This procedure has a fairly general applicability including systems with scare measurements. The stochastic modeling and analysis for hydraulic conductivity and river conductance was performed using normal distributions under 100 realizations. The results show that return flows from irrigated lands and seepage from the Zayandehrood River form significant components of the WATER budget, while boundary conditions play a minor role in the total mass balance.

SURFACE WATER QUALITY management is very important. Qualitative indicators of WATER pollution can indicate the trend of QUALITY changes over time and place. The aim of this study was to evaluate the QUALITY of Golin river using IRWQISC index. For this purpose, the Golin river WATER was sampled twice a month in a period of one year from May 2019 to April 2020 in Najar village station located in downstream of river. Different parameters which evaluated in this study were DO, pH, BOD5, COD, nitrate, phosphate, electrical conductivity, total hardness and turbidity. The results of the study using the IRWQISC index showed that the range of the index values in the warm months of the year was "between" 30.57 to 32.17 with relatively poor-QUALITY category. While in the cold months of the year the index values obtained "between" 27.36 to 27.83 with poor QUALITY category. In general, according to the results from the annual average of the IRWQISC index, the numerical value was obtained as equal to 29.62, which showed Golin river in poor QUALITY category. The results which presented in this study can be useful for different organization decision to perform their WATER related projects on Golin river.

WATER QUALITY in each area, indicates the impact of geology, climate and anthropogenic pollutants. Monitoring of WATER QUALITY in most cases result in complex data shows the perfect act of WATER RESOURCES, so they need appropriate method for analyzing. In this study hydrochemical evaluation of Hiv basin which located in west of Hashtgerd have been done. To measure the concentration of main cautions and anions, totally 12 samples from SURFACE WATER RESOURCES at the year 1393 and 1394 were collected. By Wilcox diagram which shows the capability of WATER for agriculture, the class of the WATER set in C2S1 that is suitable for farming. According to scholler diagram, WATER consumption for drinking is acceptable and also in comparing to Iran standard and International standards, it is admissible. Piper diagram which use for hydro-chemical assessments, shows that the class of WATER set in CaSO4 (anhydrite) and CaHCO3 which are for evaporate rock and hard WATER, respectively.

The main objective of this study is to develop a higher order numerical scheme to simulate the pollutant spreading in SURFACE WATER RESOURCES. The new discretisation schemes in Finite Difference Method are presented in one and two dimensional domain to predict SURFACE WATER QUALITY. Moreover, the effect of dimensionless computational numbers on numerical processing and errors is investigated for several methods. The grid size sensitivity analysis is made based on numerical results which are obtained in several methods. A real case study is made for thermal pollutant released from cooling WATER outfall of a power plant into the adjacent river. The numerical results are compared with field measurements and a good agreement is obtained.

Tehran potable WATER is mainly provided from SURFACE WATER RESOURCES including Karaj and Jajrud rivers. There are no doccumented and valid data on flouride concentration in different Tehran WATER supplies. In this study it was attempted to determine flouride concentration in SURFACE WATER RESOURCES supplying Tehran drinkink WATER. In this regard, 8 stations along the Karaj River and 5 stations along the Jajrud River have been selected and during 8 months study representative samples were taken on the basis of two months intervals. According to the study results the flouride concentrations were 0.15-0.35 and 0.28-0.52 mg/1 in Karaj and Jajrud rivers respectively. These concentrations are below drinking WATER standard limits (0.7-2.0 mg/1) and thus it is recommended to adjust flouride concentration in WATER treatment plant or to provide it through other ways such as supplementary diet programs.