Generally river water quality does not change drastically unless there are some human influence. generally two sampling one in pre-monsoon and the other on post monsoon seasons is sufficient.

you need to take a number of samples say N1 and then add another sample (few(, add them to the first so they will be N2, now do t-test and f-test for group N1 and group N2 difference in means and sd , if the differences are not significant you are ok if not then add another few samples to N2 to be N3 and test between N2 and N3 , and so on until you get insignificant means and variance differences

For systematic water quality monitoring, you have to start with monthly monitoring. After analysing the monthly monitoring data, you can decide the frequency of monitoring depending on the pattern and extent of chemical or biological quality variations. As the river discharge is directly related to rainfall and surface runoff, water quality analysis, especially with respect to bacteriological contamination, is very important during monsoon season. During pre-monsoon and post-monsoon, it will be mostly chemical contaminants due to man made pollution activities.

Dear Thapa, Suhili and Prasad, many thanks for your constructive answers and recommendation.

Dear Zelalem,

In my opinion "more frequent you do, more accurate you go". However, quarterly sampling (3-month interval) of river water would meet objectives of most of the studies. Additionally you can take samples from upstream, middle and downstream areas of the study area of the river to see if water quality changes with distance.

Zafar

In accordance with Zafar Hashmi: more frequent...! But the registration of the level-fluctuation is important. The water quality is heavily determined by the yield, and the pollution sources.

Hi! Spring flood and rain floods: on the rise of the water level - 2 samples, at the peak - 1, in the recession 2-3 (washout of the substance from the catchment of the river), summer low water - 1-2, beginning of winter -1, deep winter low - 1, before the spring high water - 1.

Addition to the above recommendations; it also depends on how much funding you have.. As Zafer Hashmi wrote "more frequent you do, more accurate you go".. So, if you have enough money, you should at least take samples monthly or once in every two weeks for detailed (year-round) WQ data to represent your study river.

Good luck..

mehmet,

I really appreciate your answers. I finally decided to collect samples once every two week. I did this based on the number of samples I am going to analyze, budget, and availability and accessibility of laboratory. Indeed my decision comes after your suggestion. I hope I will be successful. Thank you for your answers.

If you are, in fact, developing a model of some type, the number of samples required to properly estimate model parameters will depend on the time scale you're investigating. If it's average annual estimates, then perhaps every two weeks is adequate. If it's diurnal fluctuations associated with phytoplankton dynamics, then two weeks is probably not enough. Consider the processes in your model first, read the literature to develop priors regarding system behavior. Finally, consider the problem of aliasing that may be associated with a two week sampling interval.

What is the software the more useful in the realization of the slices in 3D of the Superficial géologies?

water quality modeling requires, sampling upstream and riverbed, we must identify the causes that contribute to the water quality along the river before identifying and modeling. ultimately it depends on the type of research you are conducting. You can get the bestari guidence from here :https://www.researchgate.net/publication/249322125_A_Review_of_Surface_Water_Quality_Models

(PDF) A Review of Surface Water Quality Models - ResearchGate

https://www.researchgate.net/publication/261107594_Water_quality_models_An_overview

(PDF) Water quality models: An overview - ResearchGate

https://www.epa.gov/waterdata/surface-water-quality-modeling

Surface Water Quality Modeling | Water Data and Tools | US EPA

http://facta.junis.ni.ac.rs/aace/aace201002/aace201002-13.pdf

WATER QUALITY MODELING ROLE IN ... - facta universitatis

https://files.nc.gov/ncdeq/Water%20Quality/Planning/TMDL/Modeling/Modeling%20101%20for%20FON%20stakeholder%20May09.pdf

Water Quality Modeling An Overview - NC.gov

https://books.google.com.my/books?id=iaD32zPjO3cC&pg=PA323&lpg=PA323&dq=Guidence+for+water+quality+modeling&source=bl&ots=oVsR9zfwlU&sig=ZnTuRdU22k3CXz_MlqJ1hswZyNg&hl=ms

Water Quality Modeling for Wasteload Allocations and TMDLs