Gauge Description:

The river is passable (but very scratchy) all the way down to 200 cfs. The minimum recommended for a relatively fluid run is 350 cfs. From 350 cfs to 650 cfs the river should be rated class III. Above 1800 cfs all rapids from Coliseum down blend together as one long difficult rapid. This should be considered a Class IV run at this level. Above 2400 cfs, class IV+. The reason for the maximum recommended flow to run the river set at 2800 cfs is the extreme danger of a swim on the lower half of the river. Actually any swim on Zippy's or Coliseum is dangerous in high water.
Several large lakes in its headwaters regulate the river. For this reason the Winnipesaukee runs more consistently and latter in the spring and early summer than most regional rivers. It is also less susceptible to quick rises due to heavy rains. Dams are located at the outflows of Lake Winnipesaukee, Winnisquam, Opechee, Wentworth, etc. that can regulate flows through the river. This is mainly used to control the lake levels for fall maintenance on docks, dams, and canals, and also to allow for flood control during spring runoff. The lakes are usually drawn down around Columbus day, this usually results in 3 or 4 days of low to medium water on the river. Occasionally in the spring the lakes will be drawn down further if a heavy snowpack threatens flooding. The New Hampshire Department of Environmental Services (NHDES) controls the flow on the Winni. See the NHDES website for current conditions and flow management discussion. Lochmere dam controls the flow for this section. Flows are usually stepped up or down as conditions warrant.
Also, check out the following sites.
Current watershed operations information
Winnisquam Lake operations information
Silver Lake operations information
 

Putin gage	Flow

-.2 to .3	200 ? 350 cfs		scratchy low		class III-
.3 to .7	351-500 cfs		Low			class III
.7 to 1.3	501-650 cfs		Low to medium		class III+
1.3 to 2.3      651-1200 cfs 		medium			class III-IV
2.3 to   	1201-1800 cfs		medium high		class IV-
		1801-2400 cfs		high			class IV
		>2400 cfs		very high		class IV+

Estimated chance (%) of finding the river at a good low level (~350 cfs) or higher. Scratchy low levels can be found at practically all other times.
Month............% chance.................comment
 

January ............50%....Watch out for ice shelves especially at the take out.
February............35%....Ice shelves.
March...............80%....Ice shelves wash out middle of month. 
April...............99%....Most dependable month 
May ................80%....Flows start dropping back
June................60%....Lake Winnipesaukee keeps flow going early in summer. 
July................35% 
August..............15% 
September...........10%....Lowest water month
October.............30%....Draw down of lake gives a few days of water
November............60%....Fall rains, dormant trees 
December............80%....River stays relatively ice free most of the winter. 

Be aware this is averaged out over several years. The % chance refers to the probability of finding the river running on any given day. For instance a 10% probability for September means on average you can only expect 3 days of water. One year there could be 6 days in September with water, other years none. Spring levels are usually higher than fall levels.