Can ablution and bath be done from a river full of dirt?Is swimming in it enough for a valid bath.
Dirty doesn't mean (ritually) unclean as I quoted in many questions on the site about tahara (see for example here Tahaara and waswas)! And a river is a running water so my assumption is that it can't be (ritually) unclean at all. But to find proofs from each madhab is a time killing task and IMO more or less useless.
Let me formulate my answer as a counter question: how would you be able to make a river (ritually) unclean?
My answer is I don't think this is possible at all unless you have built a barrage and used just the location of this barrage to make your ablution after filling it with large amounts of unclean things (alcohol for example: how much alcohol would you need to make the water of a river have a taste of alcohol or get the color of wine)! But if the river was full of mud or anything which is "naturally" part of it which would make it look "dirty" then this doesn't change anything on the fact that it's water is clean for a ritual washing.
Assuming that this solves the part of water of a river being clean then ablution from such a water would be valid.
But for ghusl the water needs to reach all your body and as in many customs bathing or performing ghusl means cleaning a part of a body the water reach it while you are touching or massaging the body parts.
And of course madhabs would say that the niyah or intention for the act is necessary, you'll have to have it in mind at the very start of the act.
See also quran 4:43
O you who have believed, do not approach prayer while you are intoxicated until you know what you are saying or in a state of janabah, except those passing through [a place of prayer], until you have washed [your whole body]. ...
or in 5:6
... And if you are in a state of janabah, then purify yourselves. ...
And finally to emphasize my logic there is a well known hadith comparing the five prayers to the situation of a man who lives beside a river and washes himself five times a day with the result that no filthiness will stay on him, which is quoted in some hadith collection here a version on the authorithy of Jabir ibn Abdullah and an other on the authorithy of abu Hurraira both from sahih Muslim.
A discussion of a-Shafi'is position from Ihya' 'ulum ad-Dyn
In Ihya' 'ulum ad-Dyn I found the following quote of Imam al-Ghazali on the impurity in river water (see in the linked translation book 3 "Mysteries of Purity" translated by N. A. Faris):
وأما الماء الجاري إذا تغير بالنجاسة فالجرية المتغيرة نجسة دون ما فوقها وما تحتها لأن جريات الماء متفاصلات وكذا النجاسة الجارية إذا جرت بمجرى الماء فالنجس موقعها من الماء وما عن يمينها وشمالها إذا تقاصر عن قلتين وإن كان جري الماء أقوى من جري النجاسة فما فوق النجاسة طاهر وما سفل عنها فنجس وإن تباعد وكثر إلا إذا اجتمع في حوض قدر قلتين وإذا اجتمع قلتان من ماء نجس طهر ولا يعود نجساً بالتفريق هذا هو مذهب الشافعي رضي الله عنه وكنت أود أن يكون مذهبه كمذهب مالك رضي الله عنه في أن الماء وإن قل لا ينجس إلا بالتغير إذ الحاجة ماسة إليه ...
Running water, on the other hand, when polluted with impurities, the ripples which have been contaminated with these impurities become impure, except those beneath and below, because the ripples of water are separated one from the other. Similarly, the impurities, if they should flow in the watercourse, render impure the part in which they fall as well as the part to the right and left of the part wherein they fall, if the amount of water does not exceed two pitchers. If the flow of the water, were faster than the flow of the impurities, what lies over the impurities is pure and what lies below them is impure, no matter how far it may move or how much it may be, unless it gathers in a pond or cavity the size of which is larger than two pitchers. If an amount of impure water, equal to two pitchers, should gather in one place, that water would become pure if mixed [with a larger quantity of pure water]. This is the position of al Shafi`i. I had hoped, however, that his position would be like that of Malik who held that water, no matter how meagre its amount might become, would not be rendered impure except through change [ in taste, colour, or odour], because the need for it is great ...
والخامس أنهم كانوا يستنجون على أطراف المياه الجارية القليلة ولا خلاف في مذهب الشافعي رضي الله عنه أنه إذا وقع بول في ماء جار ولم يتغير أنه يجوز التوضؤ به وإن كان قليلاً وأي فرق بين الجاري والراكد وليت شعري هل الحوالة على عدم التغير أولى أو على قوة الماء بسبب الجريان ثم ما حد تلك القوة أتجري في المياه الجارية في أنابيب الحمامات أم لا فإن لم تجر فما الفرق وإن جرت فما الفرق بين ما يقع فيها وبين ما يقع في مجرى الماء من الأواني على الأبدان وهي أيضاً جارية ثم البول أشد اختلاطاً بالماء الجاري من نجاسة جامدة ثابتة إذا قضى بأن ما يجري عليها وإن لم يتغير نجس أن يجتمع في مستنقع قلتان فأي فرق بين الجامد والمائع والماء واحد والاختلاط أشد من المجاورة
A fifth proof is found in the fact that it was the practice to perform abstersion along the edges of small bodies of running water. There is no disagreement concerning the position of al-Shafi'i that if urine should fall into running water and the water does not undergo any change [in taste, or colour or odour], it will still remain permissible to use the water for ablution no matter how small the quantity. And what difference is there between running and still water. Upon my life, which is the stronger argument: to base the decision on the lack of change in the water or on the force of its flow? Furthermore, what are the limitations of this force? Does it extend to the water which flows within the pipes of baths or not? If it does not extend to the water which flows within the pipes of baths, what accounts for the difference? And if it does extend to such water that is the difference between what falls into it and what falls into its course as it is poured out from vessels over the body, when both are running waters? Furthermore, if it is to be ruled that water which flows over a solid and stationary impurity is impure, although it does not undergo any change, and that it remains impure until a quantity equal to two pitchers collects in a small pond, [it should be remembered] that urine is intermixed with running water more readily than any solid and stationary object possibly could. And what difference is there between the solid and liquid [impurities] when the water is the same and admixture is more through-going than mere contact?
Note that al-Ghazali here is discussing a-Shafi'is position on the purity of water!
Also note that the last quote seems to underline that it is practically rather impossible to make the river water (ritually) impure.
People often confuse this matter, lets have a look at the hadees:
Abu Hurairah related that a man asked the Messenger of Allah:”O Messenger of Allah, we sail on the ocean and we carry only a little water. If we use it for ablution, we will have to go thirsty. May we use sea water for ablution?” Said the Messenger of Allah “Its (the sea) water is pure and its dead (animals) are lawful. (Al-Bukhari)
Now if it was the case that all the running waters are pure, than even the severage water would fall in this category.
We need to understand the real concept, which is, that the running water is pure until or unless something changes its:
If any one of these properties are changed considerably by any impure thing in the water of any kind, it is not pure and cannot be used for purifying. If any of these properties are changed by something pure like some soap or some oil, then this water is pure, but then there is difference of opinion some say we can use this water for purifying, and some say this water cannot be used for purifying.
Abû Umâmah al-Bâhilî relates that Allah's Messenger said: "Nothing can make water impure unless it alters the water's smell, taste, or color."
This hadîth is related in Sunan Ibn Mâjah, Sunan al-Bayhaqî, and Mu`jam al-Tabarânî al-Kabîr.
Al-Shâfî`î said: "What I said that water becomes impure if its taste, color, or scent is altered by impurities is attributed to the Prophet (peace be upon him), but its chain of transmission is not acceptable to hadîth critics. However, its meaning is agreed upon by everyone and I know of no one who disagrees on this matter." [Sunan al-Bayhaqî] (details)
There is no evidence which may suggest that all kind of running waters are pure.
But, i should mention that there is an old scholarly difference of opinion in this matter( read in above link or here). But still, to be on safe side, we should avoid the disputed matters, i.e the impure(contaminated with impurities) flowing water for purity. I am convinced with the above arguments and common sense also suggest same that this kind of water is impure. Allah knows best.