Dear Gabriel,

Sampling should be taken from the surface and riverbed soil as well. Please see the following link which may give you more information:

http://www.rgs.org/OurWork/Schools/Fieldwork+and+local+learning/Fieldwork+techniques/Rivers.htm

Hoping this will be helpful,

Rafik

Dear Gabriel,

Examples of abiotic factors include:

1.    temperature

2.    light intensity

3.    moisture content of soil

4.    pH of the environment

  For abiotic factor the the riverbed soil may be considered for sampling

same flood plain will more than likely be the most polluted place around because in tests of the river flood plains here we are finding very high levels of nitrates, phosphates, and many other pollutants that get washed down from further upriver.

 Lack of systemic data about composition of riverbed and indexes of mechanical characteristic, the influence of composition and indexes of mechanical characteristic of riverbed  consider difficultly in physical and mathematical models. Taking the typical wandering section of river cone penetration tests were carried out and indoor tests  worke out. Firstly, huge data about composition and mechanical characteristic of riverbed are achieved, it shows that the main components of riverbed in lower Yellow River are silty clay, silty loam, sandy loam, sand and so on. Secondly, physical and mechanical indexes of riverbed soil keep strong regularity. Finally, formation cause and change trend are achieved by the basic data of riverbed soil, thus it will improve the development of technology about physical model and numerical method of river.

Elemental compositions were assessed through the estimation of geochemical accumulation indices, pollution load index, the contamination factor and bioaccumulation factor (BAF), determined to reveal any potential toxic effects on biota. Significant enrichment of the soil with Cd, Zn, Cu, Ni and Pb observe in all considered sites and shows a veritable metallic polluted state. The highest concentrations of metals recorded in soil of riverbed.

 The sampling methods may include:

1.       through-depth water sampling using conventional water samplers or pumped sampling methods.

2.       long-term water sampling at fixed locations using an autonomous and programmable sampling carousel.

3.       surface grab/core sampling of bed material

Regards,

Prem Baboo

https://books.google.co.in/books?id=Czn--EP15DsC&pg=PA7&lpg=PA7&dq=river+water+sampling+including+river+bed&source=bl&ots=fNQ6PBZ2ZE&sig=T8O4kLhAKp_UZIOykJh8g7uH1Oc&hl=en&sa=X&ved=0ahUKEwisk8T1-PrNAhUMMo8KHa99BsoQ6AEINDAH

Just for you to consider as I did not read the information provided already.  Most river bottoms are not specifically soil unless the river is degrading into a previous valley soil.  Most riverbeds are alluvial/fluvial materials that are washed from the landscape or eroded from streambanks or channels, and deposited temporarily or in some instances, semipermanently.  Since clay and silt are so fine, most stream bottoms unless extremely low gradient will not have these as major fractions.  Sampling of the riverbed substrate can give evidence relative to substrates present, pollutants or hazardous materials, but these may not be equally present in all facets (ie, riffles, run, pools and glide) and may depend also on proximity of point sources.  

I would ask if there is not already some water quality sampling data already available.  I do not know your goal of sampling, is it for a long term purpose or perhaps a class project to become familiar with techniques?  I would suggest to you that sampling such a large and polluted water is not necessarily an activity for someone on a small budget or passing interest. Water quality is often affected by streamflow rate, so if you do not have a stream gauge, then at least a way to estimate river stage.  Sampling polluted waters should review methods with a person with hazardous material training, sampling, preserving and analyzing samples of various types if unknown.  If you have an agency that normally might do this sampling, perhaps you can collaborate with them.  

I have a report on Indian Creek watershed that sampled and highlights the various hydrologic conditions present from about 1995 in my researchgate listing.  This is a relatively unpolluted circumstance except for a few cattle, beaver, waterfowl, and wildlife, and not a major river, but might give you some more ideas on the abiotic subject area, importance of watershed conditions, etc.  There was no real intent in that report other than to compile and present mostly available information for further land management and planning.  

Perhaps researching available information would include some need for general water quality sampling.  But, there are so many potential abiotic elements in rivers and streams that are not being mentioned.  So determine your intent and adjust plans and title to be as specific as you can.  I do not know enough specifics to advise you in sampling such a large system so it will end up with something that makes sense and is useful beyond general reconnaissance samples.  That intent should help you decide if the sampling of the stream substrate materials is important to your results.

Knowing watershed and activity history is sometimes important.  For instance, if you dredge up some mercury in the bottom substrates, did it come from recent or past industry or was it to amalgomate gold during past mining days in the river system?  If you find hazardous materials, it may be helpful in knowing if it is a legacy or current issue to begin to compile ideas on what are the problems and perhaps eventually propose how they might be treated. 

Hello Gabriel,

For river water sampling should be done vertically at several depths up to the bottom. also go for  the river bottom core sample for detail sediment analysis. sediment may be characterized physically and chemically. C dating technique should be used to evaluate the core bed sample.