Great stuff as ever from Dac. Lots of nice clues with great surface readings, and all of them fair.

It wasn’t too difficult to spot this week’s theme! (as if we haven’t seen enough water this summer :-) A couple of the rivers are a little obscure but easy enough to determine from the wordplay. The clues today are fairy straightforward so there is no need for many comments from me.
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Across

1 JORDAN 

4 DELAWARE  DE LA MARE with M changed to W

10 MOSELLE  ELL in *(SOME)

11 POTOMAC  *(TOO) in CAMP reversed

12 AVON  A VON

13 ST LAWRENCE  R in *(NEWCASTLE)

16 THAMES  HAM in SET reversed

17 WELLAND  WELL AND - a river in East Anglia

20 VISTULA  IS in *(VAULT)

21 ROTHER  R OTHER - there are several rivers with this name in the UK

24 SHENANDOAH  SHE NAN DO A H

25 ELBE  hidden in ‘kiEL BErlin’

27 ORINOCO - easy after a recent Womble themed Indy

29 GARONNE  N in *(ORANGE)

30 DNIESTER  *(RESIDENT) - a river in the Ukraine

31 SEVERN  EVER in S N

Down

1 JAM TARTS  TART in JAM[e]S

2 RESTORATIVE  REST O[pe]RATIVE

3 ABLE  [t]ABLE

5 EXPIATES  EXP[atr]IATES

6 AFTER BLOOD  dd

7 ARM  A RM (Royal Marine)

8 EXCEED  EX CEED - homophone of ’seed’ (favourite)

9 LENTO  LENT O

14 NONCHALANCE  NO N A L in CHANCE

15 MEAT WAGONS  dd

18 GLADSOME  *(LAME DOGS) - from the hymn ‘Let us with gladsome mind’ (John Milton)

19 TREE FERN  REEF in TERN

22 ESMOND  *(DEMONS) - ‘attacking’ is not the most obvious anagram indicator, ‘upsetting’ might have been better

23 CARGO  CAR GO

26 ERNE  hidden in ‘wintER NEst’

28 ICI  dd - unfortunately one of the definitions is incorrect as ICI is no longer a British company. It has been taken over by AkzNobel, a multinational organisation with headquarters in the Netherlands.

Boatman is a name I’m not familiar with - maybe a new addition to the Guardian stable? As a result I had no idea what to expect from this puzzle, but it turned out to be fairly straightforward: nothing outstanding but a few nice clues, and a couple of niggles too.

Key:
dd = double definition
* = anagram
< = reverse

Across
1. PALLID LAP< LID
5. CAMISOLE CAM I SOLE
9. FRUIT BUN Spoonerisms again! This one is of “brute fun”. The enumeration is given as (8) but should surely be (5,3)
10. AXEMAN E in MAX + AN - the “mad axeman” being an example of one who displays berserk behaviour
11. ECOTERRORISM ERROR in (ETC I’M SO)*
13. PUNT PUN + T(ip). Groan indeed. See 6dn for another appearance by Boatman.
14. TALKBACK (BLACK MARKET less ME R). Nicely misleading definition.
17. JERRYCAN The idea here is “Tom can’t but Jerry can” - easy to solve but I don’t think the structure of the clue quite, er, holds water.
18. RIND IN in RD
20. UNCHARITABLE I in UNCHARTABLE. “Hold” is doing duty as part of the definition of UNCHARTABLE, and to indicate the inclusion.
23. GHURKA A simple hidden answer
24. BACKBONE To finance is to BACK and B1 expanded is B ONE
25. SHARP EYE (PREY AS HE)* Cleverly concealing the division between the two parts of the clue.
26. SPRITE (mothe)R in SPITE

Down
2. AFRO Hidden &lit, sort of - an Afro being a “frothy” hairstyle.
3. LEICESTER Homophone of “less to” - just about, if said as part of the phrase “less to say”
4. DEBTOR (ROT BED)<
5. CONCERTINA TABLE ONCE in INTRACTABLE*. Not sure I’ve heard this expression before, though it was easy to get with a few crossing letters. Rather a weakness that the letters of “table” occur in order in the fodder, I think.
6. MEAT ROLL ME A TROLL. Boatman is “me” in this one, as opposed to 13ac where it refers to an actual boatman.
7. STEER dd - a hint is a “steer”. Bull markets - remember them…?
8. LEAP SECOND APSE in LEÇON + (be)D. Leap seconds are added at midnight on New Year’s Eve from time to time to compensate for slight variations in the Earth’s orbit.
12. SURE ENOUGH (SEEN OUR)* + UGH
15. BURGER BAR (RE GRUB)< + BAR
16. SCARFACE SCARF ACE - Scarface is a gangster film first made in 1932 and remade in 1983 with Al Pacino in the title role.
19. ABACUS (punj)AB A CUS(tard)
21. HIKER Hidden - as in 23ac the slightly contorted wording makes this very easy to spot. The surface is vaguely relevant, as Gandhi did everything simply, and Jack Kerouac described spontaneous trips in On The Road.
22. GNAT (win)G + ANT*. Boatman seems to like using the ends of words for odd letters.