HydrionisGlobal Water Intelligence
HUC8 subbasin

Contoocook River

3 monitoring stations within this area in United States, holding 460 values between 1918 and 2026. A United States federal hydrologic unit at the eight-digit subbasin level — a drainage area, not a river. Many subbasins take the name of the largest river within them, and the gauges below are anywhere inside the area, including on tributaries.

United StatesHUC8 subbasin

The monitoring network within this area

Hydrionis holds 460 values from 3 gauges within it. Discharge is a property of a gauge and its reach, not of this drainage area, so this page reports the network and its records rather than a single figure.

3
Gauges
460
Values held
1918–2026
Record spans
Gauges within the Contoocook River huc8 subbasin
3 monitoring points, positioned as the publisher records them.
Gauges within the Contoocook River huc8 subbasinNUBANUSIT BK BLW MACDOWELL DAM NR PETERBOROUGH NH, BLACKWATER RIVER NEAR WEBSTER, NH, NORTH BRANCH RIVER NEAR ANTRIM, NHNUBANUSIT BK BLW MACDOWELL DAM NR PETERBOROUGH NHBLACKWATER RIVER NEAR WEBSTER, NHNORTH BRANCH RIVER NEAR ANTRIM, NH

Flood peaks, as measured

This gauge's flood record, as measured. Unlike a daily mean it is the discharge at the moment the river was highest, which is the figure flood frequency analysis is built on.

Largest measured flow of each year at BLACKWATER RIVER NEAR WEBSTER, NH
The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1919–2025.
Shading marks when something was recorded, not what caused the line.
Largest measured flow of each year at BLACKWATER RIVER NEAR WEBSTER, NHLargest measured flow of each year at BLACKWATER RIVER NEAR WEBSTER, NH: BLACKWATER RIVER NEAR WEBSTER, NH in m³/s, from 1919 to 2025.Hurricane Katrina water and sanitation collapse0100200300400m³/s19191937194819591970198219962008

Published by the gauge's own operator from its sub-daily record; Hydrionis stores the figure rather than recomputing it. A year the gauge did not cover produces no value rather than a low one, and the gaps are stated below the chart. A peak is a property of this gauge and its reach: a larger flood upstream or downstream of it is not in this series.

What the shaded periods are (1 event)

A shaded period marks when something was recorded, not what caused the shape of the line. Where the two coincide, they coincided.

Documented record — A documented event, compiled from cited sources after it happened. The dates are as good as the record, which for older events can mean the month rather than the day.

EventTypePeriodStandingAuthority
Hurricane Katrina water and sanitation collapseFlood2005-08-29 – 2005-09-30Documented record
Compiled record

Not shown on this chart

  • The 1976 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • The 2022 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • Yorkshire drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • Cantareira water crisis, São Paulo — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • Cape Town Day Zero — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • European drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
View the data behind this chart
Underlying data
PeriodBLACKWATER RIVER NEAR WEBSTER, NH (m³/s)
191970.2
192080.7
192750.7
192947.6
193038.5
193144.2
193258.9
193383.5
193483.5
193552.4
1936311
193768.2
1938195
193963.1
194061.7
194129.4
194254.7
194344.7
194445.6
194551.8
194639.4
194739.6
194835.4
194932.3
195037.9
195167.7
195267.7
195365.7
195459.5
195537.4
195660.3
195713.6
195860.9
195962.9
196062.9
196137.1
196264.3
196343.3
196454.1
196526.4
196629.7
196742.2
196852.7
196962.9
197047.0
197143.6
197246.7
197354.4
197438.8
197547.9
197653.2
197756.9
197956.4
198049.3
198151.5
198253.8
198347.6
198528.6
198645.3
198761.7
198842.5
198946.4
199055.8
199232.0
199359.7
199451.3
199662.3
199857.5
199949.0
200058.9
200156.4
200231.1
200352.7
200443.6
200558.6
200658.0
200755.2
200851.3
200953.5
201050.4
201157.8
201241.1
201452.1
201548.4
201642.5
202551.8

About this series

Everything below is a property of the data rather than a rating of it. There is deliberately no single confidence score: how much a gap matters depends on what you are about to do with the series, and only you know that.

Source
United States Geological Survey — National Water Information System · US Government work — public domain
How the values came to existMeasured
Period held1919–2025
Completeness80.4% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps
  • 9 separate periods inside 1919–2025 hold no value. The longest runs from 2017 to 2024 — 8 years with no reading. They are drawn as breaks in the line and are never interpolated across.
ContinuityThe record begins in 1919 and is not continuous from it: 107 years separate the first value from the last, and 80% of the years between them are held. The span is not the record.
Last read from the publisher2026-10-01
RedistributionPermitted by the upstream licences
Commercial reusePermitted by the upstream licences. No Hydrionis access tier can widen this.
MethodologyHow this was produced

How much of the rain came back out

A discharge in cubic metres per second cannot be compared with anything: the larger number may only mean the larger catchment. Divided by the area draining to the gauge it becomes a depth of water over that land, which answers a question a reader already has — of the rain that fell here, how much came back out as river?

Water leaving the catchment above BLACKWATER RIVER NEAR WEBSTER, NH, as a depth
The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1919–2025.
Shading marks when something was recorded, not what caused the line.
Water leaving the catchment above BLACKWATER RIVER NEAR WEBSTER, NH, as a depthWater leaving the catchment above BLACKWATER RIVER NEAR WEBSTER, NH, as a depth: BLACKWATER RIVER NEAR WEBSTER, NH in mm, from 1919 to 2025.Hurricane Katrina water and sanitation collapse2004006008001,000mm19191935194319511959196719751983BLACKWATER RIVER NEAR WEBSTER, NH 1919: 640 mmBLACKWATER RIVER NEAR WEBSTER, NH 1928: 626 mmBLACKWATER RIVER NEAR WEBSTER, NH 1929: 543 mmBLACKWATER RIVER NEAR WEBSTER, NH 1930: 419 mmBLACKWATER RIVER NEAR WEBSTER, NH 1931: 460 mmBLACKWATER RIVER NEAR WEBSTER, NH 1932: 530 mmBLACKWATER RIVER NEAR WEBSTER, NH 1933: 586 mmBLACKWATER RIVER NEAR WEBSTER, NH 1934: 566 mmBLACKWATER RIVER NEAR WEBSTER, NH 1935: 537 mmBLACKWATER RIVER NEAR WEBSTER, NH 1936: 678 mmBLACKWATER RIVER NEAR WEBSTER, NH 1937: 726 mmBLACKWATER RIVER NEAR WEBSTER, NH 1938: 734 mmBLACKWATER RIVER NEAR WEBSTER, NH 1939: 496 mmBLACKWATER RIVER NEAR WEBSTER, NH 1940: 602 mmBLACKWATER RIVER NEAR WEBSTER, NH 1941: 288 mmBLACKWATER RIVER NEAR WEBSTER, NH 1942: 458 mmBLACKWATER RIVER NEAR WEBSTER, NH 1943: 558 mmBLACKWATER RIVER NEAR WEBSTER, NH 1944: 503 mmBLACKWATER RIVER NEAR WEBSTER, NH 1945: 728 mmBLACKWATER RIVER NEAR WEBSTER, NH 1946: 524 mmBLACKWATER RIVER NEAR WEBSTER, NH 1947: 541 mmBLACKWATER RIVER NEAR WEBSTER, NH 1948: 467 mmBLACKWATER RIVER NEAR WEBSTER, NH 1949: 372 mmBLACKWATER RIVER NEAR WEBSTER, NH 1950: 518 mmBLACKWATER RIVER NEAR WEBSTER, NH 1951: 802 mmBLACKWATER RIVER NEAR WEBSTER, NH 1952: 714 mmBLACKWATER RIVER NEAR WEBSTER, NH 1953: 732 mmBLACKWATER RIVER NEAR WEBSTER, NH 1954: 754 mmBLACKWATER RIVER NEAR WEBSTER, NH 1955: 567 mmBLACKWATER RIVER NEAR WEBSTER, NH 1956: 569 mmBLACKWATER RIVER NEAR WEBSTER, NH 1957: 390 mmBLACKWATER RIVER NEAR WEBSTER, NH 1958: 591 mmBLACKWATER RIVER NEAR WEBSTER, NH 1959: 559 mmBLACKWATER RIVER NEAR WEBSTER, NH 1960: 726 mmBLACKWATER RIVER NEAR WEBSTER, NH 1961: 446 mmBLACKWATER RIVER NEAR WEBSTER, NH 1962: 540 mmBLACKWATER RIVER NEAR WEBSTER, NH 1963: 424 mmBLACKWATER RIVER NEAR WEBSTER, NH 1964: 388 mmBLACKWATER RIVER NEAR WEBSTER, NH 1965: 246 mmBLACKWATER RIVER NEAR WEBSTER, NH 1966: 442 mmBLACKWATER RIVER NEAR WEBSTER, NH 1967: 470 mmBLACKWATER RIVER NEAR WEBSTER, NH 1968: 552 mmBLACKWATER RIVER NEAR WEBSTER, NH 1969: 746 mmBLACKWATER RIVER NEAR WEBSTER, NH 1970: 543 mmBLACKWATER RIVER NEAR WEBSTER, NH 1971: 447 mmBLACKWATER RIVER NEAR WEBSTER, NH 1972: 737 mmBLACKWATER RIVER NEAR WEBSTER, NH 1973: 879 mmBLACKWATER RIVER NEAR WEBSTER, NH 1974: 579 mmBLACKWATER RIVER NEAR WEBSTER, NH 1975: 639 mmBLACKWATER RIVER NEAR WEBSTER, NH 1976: 661 mmBLACKWATER RIVER NEAR WEBSTER, NH 1977: 651 mmBLACKWATER RIVER NEAR WEBSTER, NH 1978: 591 mmBLACKWATER RIVER NEAR WEBSTER, NH 1979: 685 mmBLACKWATER RIVER NEAR WEBSTER, NH 1980: 369 mmBLACKWATER RIVER NEAR WEBSTER, NH 1981: 605 mmBLACKWATER RIVER NEAR WEBSTER, NH 1982: 544 mmBLACKWATER RIVER NEAR WEBSTER, NH 1983: 804 mmBLACKWATER RIVER NEAR WEBSTER, NH 1984: 695 mmBLACKWATER RIVER NEAR WEBSTER, NH 1985: 399 mmBLACKWATER RIVER NEAR WEBSTER, NH 1986: 614 mmBLACKWATER RIVER NEAR WEBSTER, NH 1987: 645 mmBLACKWATER RIVER NEAR WEBSTER, NH 1988: 478 mmBLACKWATER RIVER NEAR WEBSTER, NH 2025: 576 mm

Computed by Hydrionis from the published annual mean flow and the catchment area the station's own publisher states. It is not a water balance: the difference between rainfall and runoff is not evaporation alone but also change in groundwater storage, water abstracted and taken elsewhere, and water imported by transfer schemes — which is why a catchment can yield more runoff than the rain that fell on it without anything being measured wrongly. A different area figure rescales every value here by the ratio between them.

What the shaded periods are (1 event)

A shaded period marks when something was recorded, not what caused the shape of the line. Where the two coincide, they coincided.

Documented record — A documented event, compiled from cited sources after it happened. The dates are as good as the record, which for older events can mean the month rather than the day.

EventTypePeriodStandingAuthority
Hurricane Katrina water and sanitation collapseFlood2005-08-29 – 2005-09-30Documented record
Compiled record

Not shown on this chart

  • The 1976 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • The 2022 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • Yorkshire drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • Cantareira water crisis, São Paulo — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • Cape Town Day Zero — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • European drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
View the data behind this chart
Underlying data
PeriodBLACKWATER RIVER NEAR WEBSTER, NH (mm)
1919640
1928626
1929543
1930419
1931460
1932530
1933586
1934566
1935537
1936678
1937726
1938734
1939496
1940602
1941288
1942458
1943558
1944503
1945728
1946524
1947541
1948467
1949372
1950518
1951802
1952714
1953732
1954754
1955567
1956569
1957390
1958591
1959559
1960726
1961446
1962540
1963424
1964388
1965246
1966442
1967470
1968552
1969746
1970543
1971447
1972737
1973879
1974579
1975639
1976661
1977651
1978591
1979685
1980369
1981605
1982544
1983804
1984695
1985399
1986614
1987645
1988478
2025576

About this series

Everything below is a property of the data rather than a rating of it. There is deliberately no single confidence score: how much a gap matters depends on what you are about to do with the series, and only you know that.

Source
United States Geological Survey — National Water Information System · US Government work — public domain
How the values came to existDerived Computed by Hydrionis
Period held1919–2025
Completeness58.9% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps
  • 2 separate periods inside 1919–2025 hold no value. The longest runs from 1989 to 2024 — 36 years with no reading. They are drawn as breaks in the line and are never interpolated across.
ContinuityThe record begins in 1919 and is not continuous from it: 107 years separate the first value from the last, and 59% of the years between them are held. The span is not the record.
Inputs last read2026-10-01 · when the records this was computed from were last read from their publishers
Calculation date2026-08-24 · when the calculation method was last versioned, not a reading of any publisher
RedistributionPermitted by the upstream licences
Commercial reusePermitted by the upstream licences. No Hydrionis access tier can widen this.
MethodologyHow this was produced

Every gauge Hydrionis holds within this area

GaugeMeasuresValuesRecord
BLACKWATER RIVER NEAR WEBSTER, NHcatchment area, annual maximum river flow, mean river flow, mean river flow, water year2221918–2026
NUBANUSIT BK BLW MACDOWELL DAM NR PETERBOROUGH NHcatchment area, annual maximum river flow, mean river flow, mean river flow, water year1901921–2026
NORTH BRANCH RIVER NEAR ANTRIM, NHcatchment area, annual maximum river flow481925–2026

How these gauges were attached to this water

Assigned by the publisher to a numbered basin Every gauge here is assigned to this drainage area by its own publisher, which issues the area an official code — 01070003. A drainage area is not a river: it contains the tributaries as well as the main channel, and a gauge in it may be on any of them.

GaugeEvidenceEstablished
BLACKWATER RIVER NEAR WEBSTER, NHStated by the publisher — USGS site service, huc_cd field — https://waterservices.usgs.gov/nwis/site/ ; named from the USGS Watershed Boundary Dataset 8-digit HU (Subbasin) layer — https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/42026-10-02
NUBANUSIT BK BLW MACDOWELL DAM NR PETERBOROUGH NHStated by the publisher — USGS site service, huc_cd field — https://waterservices.usgs.gov/nwis/site/ ; named from the USGS Watershed Boundary Dataset 8-digit HU (Subbasin) layer — https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/42026-10-02
NORTH BRANCH RIVER NEAR ANTRIM, NHStated by the publisher — USGS site service, huc_cd field — https://waterservices.usgs.gov/nwis/site/ ; named from the USGS Watershed Boundary Dataset 8-digit HU (Subbasin) layer — https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/42026-10-02

What this record holds

Hydrionis decides which waters get a page, and which of those are offered to search, from what is actually held rather than from how the page reads. Five signals are counted; this record has 2 of them, which makes it a profile, not indexed.

SignalHeldCounts
Gauges holding a real record2no
Years spanned109yes, 20 or more
Values held460no
Distinct measurements4yes, 2 or more
Publishers measuring it1no
Official identifiers1recorded, not counted

Use this data

Use this data

No bulk download is offered here, which is a licence position rather than a product one: at least one contributing publisher does not permit redistribution. The values can be read on the page, cited, and pointed to at source.

Attribution and citation

Suggested citation for Hydrionis

Hydrionis (2026), Contoocook River gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-contoocook-river/

Cite Hydrionis where you rely on values Hydrionis computed, on the method that produced them, or on the compilation itself. The underlying measurements remain the publishers’ and their attribution requirements apply to you directly.

Recommended, not required. Hydrionis does not claim rights over unmodified public data it relayed, and doing arithmetic on somebody else’s measurements does not make them Hydrionis’s. Cite the version and the access date: the Contoocook River gauge records changes as publishers release and as methods are revised, and a citation without both cannot be checked later. Full guidance is on cite and reuse.

None of the contributing licences requires attribution. Crediting the publishers is still good practice and they are listed above.

Where these figures come from

MeasuredHigh confidence2025-05-14

Source: USGS — National Water Information System, USGS site 01087000, annual peak streamflow. Licence: Open.

Method: The instantaneous maximum discharge of each water year as published by USGS, dated to the day it occurred. One value per October-to-September water year; where the publisher lists both a systematic and a historic peak for a year, the larger is the annual maximum. Values the publisher marks as maximum daily averages are not held here, because they are not instantaneous peaks. Values marked as bounded rather than measured are held as censored observations carrying the bound. Cubic feet per second are converted to cubic metres per second and the publisher unit is recorded alongside.

Rating curves are extrapolated at extreme discharges, so the largest values in a peak series carry the largest measurement uncertainty. Data from the U.S. Geological Survey National Water Information System, a work of the United States government and therefore in the public domain.

Retrieved 1 October 2026.

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