The Reservoir
Essays on water-data transparency
Behind-the-scenes notes, methodology deep-dives, country case studies, and observations from building the world's first systematic ranking of reservoir-data openness.
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Introducing the Reservoir Transparency Index: H1 2026
The inaugural, semi-annual ranking of how openly countries publish their reservoir storage data. The H1 2026 edition evaluated 194 countries — and the median one scores F.
Nordic hydro reservoirs: what happens when they run low? Norway, Sweden and Finland's official alert levels and power-rationing rules explained
Norway, Sweden and Finland's official alert stages for hydro reservoirs: Statnett, NVE, Svenska kraftnät and Fingrid rules, with NVE's latest weekly fill.
Spain drought scenarios explained: the thresholds that trigger water restrictions, basin by basin
embalses.net put Spain's peninsular reserve at 57.2% on 19 October 2026 (32,062 hm³). Restrictions follow each basin's scarcity index, not that percentage.
India Water Restriction Thresholds: How Reservoir Levels Trigger Drought Alerts and Water Cuts
On 1 October 2026 the Central Water Commission bulletin stood at 71.84% of capacity, against 90.31% a year earlier and a normal level of 81.79%. Mumbai's 10% cut, in force since 15 May, was still on when the seven lakes read 92.36% on 13 October. Maharashtra ordered a minimum 10% cut from 16 October after declaring drought in 265 of 358 talukas.
What dam level starts water restrictions in Australia's capital cities?
The storage lines in each capital city's drought plan, and the latest reading from the agency that owns it. Quoted separately. Nothing is calculated.
How close is your city to water restrictions?
Official drought-plan lines and the latest agency reading for 44 US water systems. Quoted separately. No distance and no date are calculated.
US Reservoirs at Risk in October 2026: Rockies Emptied, Mead and Powell at Record Lows
Ranked by gap to their own early-October average, the sharpest US shortfalls are in the Rockies: Green Mountain is 10.8% against a 65% norm, Jackson Lake 8.1% against 56%, Blue Mesa 19% against 63%. Lake Mead is 24.2% — the lowest in our five-year record — and Lake Powell 20.8% after a new September low of 20.3%. Together they hold 22.6% of combined capacity. Full figures on the Lake Mead and Lake Powell water-level pages.
Lake Mead Water Level Today: 24.2% Full in October 2026, the Lowest in Five Years
Lake Mead was 24.2% full on 6 October 2026 — about 6.82 million acre-feet of its 28.26 maf capacity behind Hoover Dam, and the lowest reading in the five years of daily Bureau of Reclamation data we hold. The reservoir has fallen every month since peaking at 31.5% on 27 February, giving up roughly 2.06 million acre-feet since then and 1.45 million over the year. Its decline has almost flatlined only because Lake Powell upstream broke a new record low in September to hold it up: together the Colorado's two giants hold 22.6% of capacity, 12.03 million acre-feet of a possible 53.28.
Lake Powell Water Level Today: 20.8% Full in October 2026, After a New Record Low
Lake Powell was 20.8% full on 6 October 2026 — about 5.21 million acre-feet of its 25.03 maf capacity behind Glen Canyon Dam, 0.5 points above a new record low of 20.3% set in mid-September. The date that explains the year is 1 January: that was Powell's high-water mark for 2026. The entire spring snowmelt was worth 0.4 points, a single gain in May, in a reservoir built to capture the Rocky Mountain runoff. It has lost 6.1 points and about 1.51 million acre-feet in twelve months — still faster than Lake Mead downstream, because Powell is the reservoir being drained to hold Mead up.
Karnataka Reservoir Levels, October 2026: 65% Full — Krishna Banked, KRS at 47%
Karnataka's 18 major reservoirs are 64.8% full at the start of October. Almatti is 80.7% and Hidkal 95%, but Krishnaraja Sagar (KRS) is 47% against 96% a year ago. The Cauvery group has fallen from 74% in August to 47%. Thirteen dams with a late-September reading in both years are 35 points behind 2025.
US Reservoir Levels, October 2026: 53.6% Full — Tied with 2022, 12 Points Below 2023
On a fixed basket of 309 reservoirs, early October 2026 storage was 53.6% of capacity — essentially tied with 2022 (53.4%) and down from 65.7% in 2023, 63.0% in 2024 and 58.8% in 2025. Colorado is 23 points below its 4-year October average; Blue Mesa is at 19%.
Five Yakima Basin Reservoirs, September 2026: 20% Full — 2.3 Times 2025, Half of 2022
The five Yakima storage reservoirs held 264 million cubic metres on 29 September 2026, 20.1% of capacity. That is 2.3 times the 115 million cubic metres of a year earlier, and half the 533 million cubic metres of 29 September 2022. Rimrock and Kachess hold the gain. Cle Elum, the largest, is at 6.4%.
Madhya Pradesh Reservoir Levels, September 2026: 76% Full as Indira Sagar Recovers, Still 7 Points Behind Last Year
Madhya Pradesh's 12 major reservoirs were 76.3% full in the CWC bulletin of 17 September 2026, up 35 points from 40.9% on 6 August. Indira Sagar, India's largest reservoir (431.6 TMC), climbed from 31.5% to 84.6%. The state is 7.5 points behind the same week in 2025 (83.8%); the remaining shortfall sits on Gandhi Sagar and Tawa, not an empty Narmada valley. Three dams are full. Dam-by-dam table with capacities in TMC and MCM.
California Reservoir Levels, September 2026: 61% Full — Almost Double 2021, but the Lowest Since 2022
California's monitored reservoirs were 61.4% full in mid-September 2026. That is almost double the 2021 level, but the state's stored-water cushion has declined in each September since 2023.
US Reservoir Levels by State, September 2026: Colorado 26 Points Below Normal
Across 332 comparable reservoirs, US storage was 54.3% full in September 2026 against a recent norm of 61.6%. Sixteen of 19 states were below their own 2022–2025 baseline, led by Colorado, North Dakota, Wyoming and Oregon.
Cyprus Reservoir Levels, September 2026: 39% Full, but Achna at 1%
Cyprus's 21 tracked reservoirs held 116.1 hm³ on 10 September 2026 — 38.7% of capacity and close to their September norm. Kouris was near normal, but Achna was at 1.2%. Several nearly full mountain reservoirs hold too little water to close the gap.
The Indian Reservoirs That Filled Fastest in 2026: Veer Dam 18% to 100% in One Week
Veer Dam in Maharashtra went from 17.5% on 2 July 2026 to 99.8% on 9 July — 219 hm³ in one CWC bulletin. Khadakvasla did 15.4% to 99.0% the same week. Mulshi added 331 hm³, the most water. Jeedipalli in Andhra Pradesh went 38% to 98% in mid-August. Same-source weeks only.
The US Reservoirs That Filled Fastest in 2026: Toronto Lake +49 Points in a Day
Toronto Lake in Kansas jumped from 33.5% on 25 June 2026 to 82.2% the next day and was full on the 27th. The same storms filled Hulah, Copan and Kaw in Oklahoma — Kaw added 381 hm³ in a week. Lake Corpus Christi then climbed from 37% to 87% in the first week of August.
September 2026 Reservoir Levels in our 15 countries: 52% average — South Africa at 96%, Lake Powell at 21%
The 1,913 reservoirs we track with a current volume reading held 52.2% of capacity in early September 2026. That average is not a climate. South Africa is 95.8% full. Lake Powell is 20.5%. India closed the monsoon at 61% and is still 10 points behind last year. Spain is 64%; Cyprus is 39%. Norway's south is 46% while the north is 91%.
India Reservoir Levels, September 2026: 61% Full, Still 10 Points Behind Last Year
India's monitored reservoirs held 61% of capacity on 3–4 September 2026 — 144 km³ across 307 reservoirs — after rising from 22% in early July. On a like-for-like basket the country is 10 points behind 3 September 2025. Madhya Pradesh and Indira Sagar have recovered; the remaining hole is the Cauvery (KRS 54% against 97% last year, Lower Bhawani 17% against 100%), plus Bhakra at 61% against 90%.
Bhakra Dam Water Level, August 2026: 53.9% Full as BBMB Tells Punjab, Haryana and Rajasthan to Cut Draws
Bhakra was 53.9% full on 20 August 2026 — 3,356 MCM, about 118.5 TMC of live storage. That's the CWC bulletin. The next day BBMB told Punjab, Haryana and Rajasthan to stop overdrawing. The dam is still filling: it was 21.4% on 2 July. Last mid-August it was at 70%, and a week later they opened the floodgates. Pong is 61.9%. Together they hold 1,994 MCM less than a year ago.
When India's Monsoon Ends, the Number Stays. 57 Reservoirs Have Already Missed Their Window
On 13 August 2026 Lower Bhawani was 24.1% full — where it started the monsoon — and in our CWC history this dam typically falls after mid-August. Add each reservoir's typical mid-August to late-September change from 2023–25 to the current reading, and 57 of 133 still miss their own September/October normal by five points or more. Indira Sagar projects to 57% against a 94% October normal. Koyna, Ujjani and Almatti have already banked the year. Tamil Nadu still has the northeast monsoon; Rajasthan and the Narmada do not.
Karnataka Reservoir Levels, August 2026: 69.3% Full as Almatti Goes From 3% to 92%
Karnataka's 18 major reservoirs were 69.3% full in the CWC bulletin of 13 August 2026, up 55.3 points from 14.0% on 2 July. Almatti, the state's largest dam, went from 2.9% to 92.4%; Tungabhadra from 3.3% to 82.7%, of which 31 points arrived in a single week. Krishnaraja Sagar (KRS) is 56.2% against 98.6% a year ago. On 13 dams with both years, the state is 61.1% now against 86.0% on 14 August 2025. Dam-by-dam table with capacities in TMC and MCM.
Mediterranean Sea Hits 33°C, 1.15°C Above the 2024 Record. Spain's Reservoirs Are 66% Full
Spain's reservoirs were 66.2% full on 18 August 2026 — 37.1 of 56.5 km³, some 13 points above the August normal — as the Sa Dragonera buoy off Mallorca logged 33.02°C, 1.15°C above the 12 August 2024 record that preceded Storm Boris and the Valencia DANA. The Mediterranean supplied about 78% of that flood's moisture; this year's sea is hotter. The basins that would receive the rain are not where they were: Catalonia's internal reservoirs are at 80% against 28% on DANA day, the Segura at 54% against 15%, the Júcar at 56%. Tous, the lower-Júcar flood dam, is still only 24% full.
The 10 Biggest Movers in India's Reservoirs, Monsoon 2026: Rengali Up 2,475 hm3, Lower Bhawani Gains Nothing
Between mid-May and mid-August 2026, 88 of the 121 Indian reservoirs we track through the monsoon rose and 25 fell, adding a net 27.5 km3. But in a monsoon almost everything rises, so each reservoir is measured against what it normally does across the same three months — and 68 of the 93 with a usable baseline are running below their own normal, by an average of 11.0 points. Rengali in Odisha added 2,475 hm3, more than any reservoir in India, climbing from 14.2% to 76.8% after falling to empty in early July. Lower Bhawani in Tamil Nadu normally gains 72.5 points across this window and this year gained none, finishing at 24.1% against 100% a year ago. Bisalpur, which supplies Jaipur, sits at 68.7% against 98.4% last August. Ten reservoirs, a paragraph each, with volumes in hm3.
The 10 Biggest Movers in US Reservoirs, Summer 2026: Corpus Christi Up 80 Points, Jackson Lake Down 49
Between mid-May and mid-August 2026, 313 of the 449 US reservoirs we track fell and only 97 rose — a net loss of 18.6 km3 and a drop in weighted storage from 64.5% to 58.9%. Lake Corpus Christi in south Texas gained 80.3 points, from 11.2% to 91.5%, the highest reading in our four-year record and a level it reached from a low set the same spring. Jackson Lake in Wyoming gave up 49.4 points and 516 hm3 against a 69.3% August normal. American Falls in Idaho lost more water than any other reservoir, 1,090 hm3, yet drew down less steeply than it usually does. Every reservoir is measured twice: the raw 90-day move, and the same calendar window in prior years, so seasonal irrigation drawdowns are separated from genuine anomalies. Ten reservoirs, a paragraph each, with the volumes in hm3 and acre-feet.
Maharashtra Reservoir Levels, August 2026: 83.2% Full as the Ghats Dams Go From Empty to Overflowing
Maharashtra's 35 major reservoirs were 83.2% full in the CWC bulletin of 13 August 2026, up 64.7 points from 18.5% on 2 July — a complete reversal of the July picture. Koyna has gone from 10.9% to 96.8%, Mulshi from 9.6% to 95.5%, and Ujjani, the state's largest dam at 123.3 TMC, from dead storage to 95.0%. Marathwada's Jayakwadi is 95.1% full against a 51% August average. The state is 3.9 points ahead of last year on a like-for-like basis, against a national figure of 51.3%. Twenty-two of the 35 dams are above 90%; the laggards are Upper Wardha in Vidarbha (56.4% against a 78% average) and the Manjara sub-basin. Dam-by-dam table with capacities in TMC and MCM.
Madhya Pradesh Reservoir Levels, August 2026: 40.9% Full as the Narmada Refills, Still 26 Points Behind Last Year
Madhya Pradesh's 12 major reservoirs were 40.9% full in the CWC bulletin of 6 August 2026, up 11 points in five weeks from 29.7% in early July — the monsoon has reached the Narmada catchment at last. Indira Sagar, the largest reservoir in India by capacity (431.6 TMC), has more than doubled to 31.5%, and Tawa rose 9.9 points in a single week to 23.5%. But the state was 67.4% full on the same week in 2025, so it is 26.5 points behind last year and about 32 points below its August average. The five Narmada-basin dams, 55% of the state's capacity, are only 26.9% full; Gandhi Sagar on the Chambal (62.3%) is the only major dam at its normal level and the only one ahead of last year. Dam-by-dam table with capacities in TMC and MCM.
Reservoirs vs Desalination, Reuse and Groundwater: The Pros and Cons of Dams in 2026
A reservoir is still the only way to bank a year's worth of water for a whole region at roughly 0.1–0.5 kWh per cubic metre, and the only water asset that also absorbs a flood and balances a grid — dams supply the water for 30–40% of the world's irrigated land and about 14% of its electricity. It is also a depreciating asset: large dams have already lost an estimated 13–19% of their original storage to silt and are headed for 26% by 2050, evaporation takes some 13% of the entire Colorado River each year, and an Oxford study of 245 large dams found an average cost overrun of 96%. This is the side-by-side ledger against every alternative — seawater desalination at 3–4 kWh/m³, advanced recycling at 1–1.5, managed aquifer recharge, long-distance transfer and the cheapest water of all, the leaks you stop — plus the five questions that decide which one a given basin should build next.
Puerto Rico Is Rationing Water in San Juan. Here's What Its Reservoir Levels Show
Puerto Rico began rotating 48-hour water shutoffs across parts of San Juan on 7 August 2026. Carraizo, the reservoir supplying the rationed area, stood at 37.49 m on 9 August — its fourth-lowest reading for that calendar day in 37 years, and lower than 92% of all August days on record. Yet it is 3.63 m above where it sat during the 2015 rationing, and La Plata, the metro's second source, is close to normal. This piece reconciles those facts: elevation is not volume, and Carraizo has taken on 4.39 million m³ of sediment since it was last dredged, so the same metre-mark holds less water than it used to. It also shows that the island's most extreme readings — Patillas and Fajardo — are outside the rationed zone entirely.
El Niño and the World's Reservoirs: What a Strong 2026–27 Event Means for Water Levels
A strengthening El Niño — under a formal NOAA advisory, with the Niño-3.4 index at +1.2 °C in early July 2026 and an 81% chance of a very strong event by October–December — is now the single climate signal most likely to reshape reservoir levels worldwide over the next year. El Niño does not add or remove water globally; it moves where the rain falls, tilting the odds toward a weaker Indian monsoon and drought across Southeast Asia, eastern Australia, southern Africa and the northern Andes, while pushing wetter winters onto the southern United States and southeastern South America. This explainer maps the mechanism region by region onto the reservoirs we track — from India, already 14 points behind last year, to South Africa's near-full dams facing their next wet season — and is careful about the catch: these are statistical tendencies, not forecasts for any single dam.
India Reservoir Levels, Week of 6 August 2026: The Biggest Refill Week Yet Adds 15 km³ as the Monsoon Reaches the South
India's tracked reservoirs added 15.0 km³ of water in the week to 6 August 2026 — the biggest weekly gain of the monsoon — as same-source Central Water Commission readings across an identical 156-reservoir set rose from 36.2% to 43.0% full. The refill finally reached the southern basins that had spent the season emptying: Srisailam leapt from 19% to 64%, Krishnaraja Sagara from 22% to 47% and Tungabhadra from 26% to 51%, while Telangana, Karnataka and Gujarat each added 14 to 18 points at the state level. 106 of the 156 tracked reservoirs rose and only 11 fell — and for the first time this season the gap to last year narrowed, from 17 points behind 2025 to 14, though Nagarjuna Sagar remains at 3% of live storage and Hirakud fell 15 points on flood releases.
South Africa Reservoir Levels, August 2026: 95.9% Full Nationally, but Cape Town's Winter Refill Is Behind Last Year
South Africa's monitored dams held 95.9% of their combined capacity on 3 August 2026 — about 28 km³ behind 216 reporting dams, and barely changed from a year earlier. The stability is an illusion of averaging: Limpopo gained 12.1 points year-on-year, with Middel-Letaba climbing from 6.5% to 99.0% full, while KwaZulu-Natal lost 9.1 points and the Northern Cape 9.5. The number that matters most is in the Western Cape, where DWS's winter-rainfall zone was 76.4% against 79.8% the same week in 2025 and the Cape Town supply system 77.9% against 84.5% — a six-point shortfall opening up with only weeks of the wet season left to close it. In the Eastern Cape, the Algoa system that supplies Gqeberha is full again at 100.2%, up from 67.9% a year ago.
India Reservoir Levels, August 2026: 41% Full, but 20 Points Behind Last Year
India's monitored reservoirs held about 41% of capacity on 4 August 2026 — roughly 97 km³ across 313 reservoirs — after the fastest four-week refill of the year, up from 22% in early July. Measured against the same reservoirs on the same date in 2025, however, storage is 20 points lower, and 93 of 133 comparable dams are below last year. The deficit is concentrated in central India, the Krishna and Cauvery basins and eastern Rajasthan: Indira Sagar, the country's largest reservoir, is 56 points down, while Maharashtra at 76% and Odisha are ahead of last year.
US Reservoir Levels, August 2026: Third Straight Year of Decline
Federally monitored US reservoirs held about 55.3% of capacity on 4 August 2026 — roughly 144 km³ across 464 reservoirs in 38 states. Measured like-for-like it is the third consecutive annual decline: on a fixed basket of 290 reservoirs, early-August storage has gone from 61.6% in 2023 to 49.2% now, and 211 of 304 comparable reservoirs are below last year. The decline reaches the giants — Lake Powell is down 8.2 points on the year and Lake Mead 3.3 — but the sharpest losses are upstream in the Colorado headwaters and the Snake basin, with Blue Mesa down 38 points and Elephant Butte on the Rio Grande at 1.3%.
North Platte Reservoir Levels, August 2026: Pathfinder Is Down to 19.8%, Less Than Half of Last Year
Pathfinder Reservoir, the largest water bank on Wyoming's North Platte River, was 19.8% full on 29 July 2026 — 202,000 acre-feet against the 452,000 it held a year ago, and the lowest start-of-August reading in our five-year record by 23 points. It is not alone: seven of the nine reservoirs in the federal North Platte chain are at five-year lows for the date, including Winters Creek Lake in the Nebraska panhandle at 21%, nearly 38 points below its previous worst. The three reservoirs that actually bank water for this river hold 720,000 acre-feet of 2.49 million — 29% full, and 456,000 acre-feet lighter than last August. That shortfall is larger than the entire remaining seasonal supply the Pathfinder Irrigation District reported on 10 July, which is why the district, serving more than 100,000 acres across eastern Wyoming and the Nebraska panhandle, warned its water could run out in the first week of August.
Colorado River Water Cuts, 2026: The 20% Reduction Measured Against What Is Left in Mead and Powell
Arizona, California and Nevada must cut Colorado River use by roughly 20% over the next two years under the final federal plan the U.S. Bureau of Reclamation published on 31 July 2026 — a framework running through 2036 that allows Lower Basin shortages of up to 3.0 million acre-feet a year. Set against the water actually left, the scale becomes clear: in the twelve months to 28 July 2026, Lake Mead and Lake Powell lost 3.04 million acre-feet between them, almost exactly the deepest single-year cut the plan permits. The two reservoirs now hold 12.5 maf, 23.4% of combined capacity — Mead at 25.0%, Powell at 21.6%. The first phase of cuts, roughly 1.3 maf a year, offsets under half of the past year's decline. And the largest deficit in the basin is not in a state facing mandatory cuts at all: Colorado's Blue Mesa is 32% full against a July norm near 70%.
New Zealand Hydro Lake Levels, July 2026: The South Island Lakes Are Nearly Full
New Zealand's hydro lakes were running close to record levels for late winter. In the week of 27 July 2026, national hydro storage was 3,598 GWh — 39% above its 93-year average for the date and 96% of the way up the full 1927-2025 range. Lake Te Anau sat at 202.77 m, the very top of its consented operating range, and Lake Pūkaki, the country's largest single store, at 531.42 m. The South Island, which holds almost all of New Zealand's controllable storage, was at the top of its recorded range for the date. Because New Zealand reports its lakes as stored electricity (gigawatt-hours) rather than water, these figures are, in effect, the charge level of the country's largest battery.
US Drought Monitor, July 2026: 38% of the Country Is in Drought — and What the Reservoirs Add
About 38% of the United States was in drought as of the U.S. Drought Monitor's 21 July 2026 reading — 45.8% of the Lower 48, an area home to roughly 114 million people — with a wider 55% at least abnormally dry and 45 states under some moderate drought or worse. That is the official weekly map of where the country is dry. It is not the same map as where the country's water is short: across the ~515 major reservoirs we track, US storage is about 62% full. The two diverge in ways that matter. The fastest deterioration is a hot flash drought across the Northern Plains and Upper Midwest — the Dakotas, Minnesota, Wisconsin — where the big reservoirs are still 80%+ full, because storage lags the weather by months. The emptiest water bank is the Southwest, where the Monitor and the reservoirs agree: New Mexico's reservoirs ~25%, Nevada's ~28%, and the Colorado River's Lake Mead and Lake Powell at 25% and 22%, near record lows. The Drought Monitor tells you where it is dry today; reservoir levels tell you where the water is already spent.
Lake Mead and Lake Powell Water Levels, July 2026: The Colorado River's Two Giants Are Near Record Lows
The two largest reservoirs in the United States sit on the same river, and both are running near empty. As of 21 July 2026, Lake Mead — behind Hoover Dam — is 25.1% full and Lake Powell, behind Glen Canyon Dam upstream, is 21.8% full, together holding about 23.5% of their combined 65.7 km³ capacity. Powell is the sharper emergency: at its lowest late-July level in five years and within a point of its 2023 record low, some 10 points below its July norm after another weak Rocky Mountain snowpack — and this low in the month it is normally fullest. Mead, at 25.1%, is all but tied with its summer-2022 record and drifting lower through the draw-down. These two hold most of the Colorado River's storage, the water bank for roughly 40 million people, and it is a quarter full — which is exactly why Arizona reads a comfortable 84% while Nevada reads 29%: the full-looking reservoirs downstream are held near the top by design, and the real water is here.
India Reservoir Levels, Week of 23 July 2026: Monsoon Refill Lifts Storage to 31% as the Rains Move East
India's tracked reservoirs added 7.2 km³ in the fourth week of July, lifting the same-source national fill from 27.9% to 31.2% between the Central Water Commission's July 16 and July 23 bulletins. Where last week's gains were concentrated in Maharashtra's Pune-area dams, this week the monsoon band did its clearest work in the east and centre: Hirakud (Odisha) jumped 30% to 41%, Hasdeo Bango (Chhattisgarh) 59% to 73%, and the northern giants Bhakra and Pong added three points each. 88 of 149 reservoirs rose. The exception is the southern Krishna basin, where Nagarjuna Sagar sits at 3.2% of live storage — the emptiest big reservoir in the country — and Andhra Pradesh's tracked set is still losing water. At 31% full, national storage has climbed about ten points off its pre-monsoon floor over two strong weeks, with the back half of the monsoon still to run.
Colombia Reservoir Levels, July 2026: 79% Full — the Country's Battery, and Bogotá's Tap
Colombia's hydropower reservoirs are 79% full as of 21 July 2026 — 13,822 of 17,440 GWh of storable electricity, a shade above the mid-July norm and about 1.5 points below a year ago. In a grid where hydropower is roughly two-thirds of generation, that number is a power-price gauge before it is a water gauge: XM publishes it daily, and it is the same figure that nearly triggered rationing during the 2023–24 El Niño. The two giants carry it — El Peñol–Guatapé at 90.5% and Guavio at 97.3%, together a quarter of national storage. The soft spot is the Chingaza system that supplies Bogotá's drinking water, in the 60s — the one large storage where a low reading is a water-supply story, not just a power one. With XM flagging renewed El Niño alerts in May 2026, the number to watch is what the reservoirs hold going into the dry season.
Taiwan Reservoir Levels, July 2026: Comfortable Now, but Watch the Typhoons
Taiwan's reservoirs are in comfortable shape in mid-July 2026 — a quiet contrast to the island's 2021 water emergency. The reservoirs supplying its biggest cities are well-stocked: Zengwen, the largest in the country and the backbone of Tainan and Chiayi, sits near 77% of effective capacity; Feitsui, which supplies Taipei, is around 80%; and Shimen, serving Taoyuan and Hsinchu, is essentially full. The one striking outlier is the small Agongdian reservoir near Kaohsiung, under 5%. Taiwan's Water Resources Agency publishes daily open data — ranking the island 4th of 167 countries on the Reservoir Transparency Index — but the numbers hide a slow-burning problem: decades of sedimentation have cut usable storage sharply (Zengwen has lost nearly 40% of its design capacity to silt), and the island depends on a handful of typhoons each year to refill. The real risk is volatility, not today's level.
South Africa Stopped Publishing Its Reservoir Data — What We Can and Can't See
South Africa — the country that gave the world the phrase "Day Zero" — has stopped publishing its national reservoir data. As of 21 July 2026, the most recent nationwide bulletin from the Department of Water and Sanitation (DWS) covers readings dated 29 June 2026, roughly three missed weekly updates ago. The last figures were reassuring — every province above 88% except a healthy Western Cape near 77% — but that is the problem: no one outside DWS can now independently confirm what South Africa's dams are doing. This is a transparency failure, not (yet) a water failure, and it exposes the weakness the Reservoir Transparency Index has always flagged: South Africa publishes through a single fragile web page with no public API, so when the page stalls, the data simply disappears from public view.
Which Regions Are Closest to Day Zero? Checking All 11 Countries We Track (2026)
"Day Zero" — the date a city's taps run dry — was coined in Cape Town in 2018. Eight years on, we checked all eleven countries we track for regions near the same fate. The honest answer as of mid-July 2026: no tracked region faces an imminent, taps-about-to-close Day Zero, and the region that invented the term has recovered to about 77% full. But the structural pressure is real and concentrated. The US Southwest is living through a slow, managed shortage on the Colorado and Rio Grande — New Mexico, Nevada and Utah are the driest states and Elephant Butte on the Rio Grande sits at roughly 2% of capacity. India's southern states face the same monsoon gamble every summer, and Spain's southeast and southern Taiwan are the catchments most likely to tighten first. This is the data-led watchlist — and why an empty hydropower reservoir is not a Day Zero.
Where Reservoir Data Comes From: The Official Source in Every Country We Track
There is no single global database of reservoir levels — every country publishes its own, through its own agency, in its own units, and the gap between the best and the worst is enormous. Australia's Bureau of Meteorology and Taiwan's Water Resources Agency offer clean open APIs you can query from anywhere; India's Central Water Commission hides the same numbers behind a weekly PDF, a geo-block and a login; and Colombia and Norway report their reservoirs as stored energy rather than water. This is the directory of the official reservoir-data source in each of the eleven countries we track — what it publishes, how often, and how open it actually is — and the raw material behind our Reservoir Transparency Index.
Day Zero: The Cities That Nearly Ran Dry, and How to Avoid the Next One
"Day Zero" — the day a city shuts its taps and rations water at collection points — was coined in Cape Town in 2018, which defined it as its dams falling below 13.5% of capacity. Cape Town never reached it, but the countdown has since run in city after city: Chennai's reservoirs fell to 0.2% full in 2019, Monterrey actually lost its taps for weeks in 2022, Montevideo blended salt water into its supply in 2023, and Bogotá rationed nine million people for a year in 2024–25. Day Zero is a demand-vs-storage failure, not a freak of weather — and a Nature Communications projection has the number of large cities facing water scarcity rising from 193 in 2016 to 292 by 2050. It is also avoidable: Cape Town escaped mainly by halving demand. Here is the roster of who came closest, why it is spreading, and the four-lever playbook — cut demand, publish the data, diversify supply, stop the leaks — for avoiding the next one.
Water Reuse and Fewer New Reservoirs: Why the Shift Spares the Ecosystem
In the water-stressed rich world, the next unit of supply increasingly comes from reusing water already used once, which lets a country build fewer new reservoirs to cover the same demand — and that shift is the ecosystem-preserving one. The economics drive it: the best dam sites are taken, and a reservoir is a depreciating asset that silts up (large dams are on track to lose ~26% of storage by 2050) and evaporates (about 13% of the entire Colorado River each year). Reuse is proven and rainfall-independent — Israel recycles ~90% of its wastewater, Singapore's NEWater meets ~40% of demand, Orange County purifies 130 million gallons a day, Windhoek has drunk recycled water since 1968. Meanwhile the US removed 108 dams in 2024, tied for the most ever. Reuse keeps the water loop inside the city, so rivers stay connected, deltas stay fed, and no new valley is drowned.
Spain Reservoir Levels, July 2026: 77% Full and Well Above Normal as the Drought Breaks
Spain's reservoirs are about 77% full in mid-July 2026 — roughly 43.2 of 56.5 km³ across the 374 reservoirs in the national bulletin, and well above the ~60% ten-year July average, about 6 points up on a year ago. The drought that gripped the peninsula from 2022 to 2024 has decisively reversed: every major river basin is above 58% full, and the Atlantic-draining west and centre are brimming. Even the historically driest corner, the Mediterranean southeast (Segura ~58%, Júcar ~63%), is only relatively low, while Catalonia — under emergency restrictions in early 2024 — is back to about 88%. As of the 6 July 2026 reading, the story is not scarcity but an unusually comfortable summer starting point.
Nevada Reservoir Levels, July 2026: 29% Full, and That's Almost Entirely Lake Mead
Nevada's tracked reservoirs read about 29% full in mid-July 2026 — near the bottom of everything we track, second only to New Mexico. But almost the entire figure is one reservoir: Lake Mead, the Colorado River giant behind Hoover Dam, holds about 94% of the state's tracked capacity and sits at just 25.4% on 11 July — effectively tied with 2022 for its lowest early-July reading in five years. Strip Mead out and the rest of Nevada averages about 77%, yet five of the seven reservoirs we track are below their mid-July normal, and Wild Horse in the northeast has fallen from 88% to 40% in a single year. Same Colorado River water Arizona depends on, filed in Nevada's column — which is why Nevada reads 29% and Arizona reads 84%.
Cape Town Dam Levels, July 2026: The Big Six Are 77% Full and Still Filling
The Western Cape Water Supply System — the six big dams behind Cape Town's taps — was 77.3% full on 6 July 2026, up 2.4 points in a week and still filling through the winter rains. Theewaterskloof, the largest, sits at 77%; Berg River has climbed to 89%; and Wemmershoek and Upper Steenbras are effectively full. Eight years after 'Day Zero,' here is how full Cape Town's dams are now, dam by dam — and why the City's own weekly figures run a week ahead of the national bulletin.
Pakistan Reservoir Levels, July 2026: Tarbela Fills Fast on the Monsoon, Mangla Lags Behind
Pakistan's three big federal reservoirs are about 68% full as of 11 July 2026 — roughly 15.6 of 23.1 km³ — but the single figure hides the year's central fact: the monsoon has arrived hard on the Indus and barely at all on the Jhelum. Tarbela, the Indus giant, has filled from about 23% on 26 June to 73% on 11 July, a 50-point rise in a fortnight that pushes it above its usual July level. Mangla, on the Jhelum, has hardly moved: at 44.7% it sits some 25 points below its July norm, its catchment still waiting for the rain. One country, two rivers, two monsoons — straight from IRSA's daily readings.
India Monsoon Tracker: Reservoirs Added 11.6 km³ in the Week to July 9, 2026
India's tracked reservoirs added 11.6 km³ of water in one week — same-source CWC bulletin readings across an identical 145-reservoir set rose from 20.6% to 26.1% full between July 2 and July 9, 2026, with 103 of 145 reservoirs rising. The turnaround is a weather map: Maharashtra's Western Ghats dams gained 20 points of weighted fill — Khadakvasla, Pune's water supply, jumped from 15% to 99% in seven days — and Karnataka added 12, while Andhra Pradesh, Telangana and Uttar Pradesh stayed flat or fell. One strong week narrows but does not erase the deficit: 26% is still low for mid-July.
Norway Reservoir Levels, July 2026: 63% Full, With the Exporting South Running Behind
Norway's hydropower reservoirs are 63% full as of July 5, 2026 — about 5.6 points below the five-year July average and the second-lowest early-July level since 2022. The headline hides a sharp split: Northern Norway (NO4) is at 86%, twelve points above its norm, while the export-facing south runs lean — NO2 South-West, the country's largest storage area and home of the interconnectors to Germany and the UK, is at 52% and flat week-on-week, and Central Norway has fallen 31 points in a year, from 87.1% to 56.4%. Measured in energy, the national system holds 55,073 GWh of a possible 87,438 — the level of Northern Europe's battery, straight from NVE's weekly Magasinstatistikk.
Maharashtra Reservoir Levels, July 2026: The Western Ghats Dams Are Unusually Empty
Maharashtra's major reservoirs are only about 18% full as the southwest monsoon works up the country in July 2026 — one of the lowest readings of any large Indian state, with 15 of 32 big dams below 20%. The deficit is deepest in the Western Ghats, where the high-rainfall storages that normally fill first are furthest from normal: Koyna is around 11% against a ~63% July norm, and Pune's Mulshi and Mula near 9%. Mumbai's Bhatsa and Marathwada's Jayakwadi sit around 28%, and Ujjani, the state's largest dam, has reached dead storage. The whole story is how far behind the rains are running.
Madhya Pradesh Reservoir Levels, July 2026: India's Largest Reservoir Is Only 15% Full
Madhya Pradesh's major reservoirs are about 30% full in early July 2026, but the middling headline hides an empty Narmada valley. Indira Sagar, the largest reservoir in India by capacity, sits at about 15% — less than half its early-July norm — while Bargi is near 12% and Tawa just 5%. The state average is held up by the Chambal's Gandhi Sagar at about 61%, above its norm. The big Narmada dams are at their seasonal floor and running below normal, barely moving week to week as the southwest monsoon has yet to fill their catchments.
Karnataka Reservoir Levels, July 2026: The Krishna and Cauvery Dams Are Nearly Empty
Karnataka's major reservoirs are only about 18% full as the southwest monsoon begins in July 2026 — among the lowest readings of any major Indian state, with 11 of 16 big dams below 20%, and the aggregate held up by two full smaller dams. The state's biggest storages are close to empty: Almatti on the Krishna at ~3% and the Cauvery's Krishnaraja Sagar, which supplies Bengaluru, at ~7%, each a fraction of its normal early-July level. Week over week the big dams are barely moving — the monsoon rains have not yet reached the catchments that fill them. For Karnataka, the whole story is the wait for the rain.
South Africa Reservoir Levels, July 2026: 96% Full, but the Western Cape Runs on a Different Clock
South Africa's dams are about 96% full as of the 29 June 2026 bulletin — an unusually high reading, with the summer-rainfall interior near 100% after a strong wet season and zero dams in the critical band. The exception is the Western Cape, Cape Town's winter-rainfall catchment, at about 76% and still filling: Theewaterskloof is around 76% and rising, and the Berg River dam jumped to ~85% in a week. It is the seasonal-inversion story — most of the country has already banked its water while one corner is still collecting it.
Australia Reservoir Levels, July 2026: The Murray Is Refilling, the Darling Is Not
Australia's reservoirs hold about 59% of capacity in early July 2026 — flat since mid-June, but the flat number hides the year's big seasonal handover. The winter refill has started on the Murray side: Hume climbed from ~29% to ~38% in a little over a fortnight and Blowering jumped almost ten points. The Darling side missed out — Lake Menindee kept falling, to about 8% against a recent July average near 57%, and Burrendong has barely moved — while the tropical north began its scheduled dry-season decline from full. The refill is a direction, not a recovery, and so far it is refilling the half of the inland that was already less dry.
Colorado Reservoir Levels, July 2026: 60% Full at the Year's High-Water Mark
Colorado's reservoirs are about 60% full in early July 2026 — but that is the annual high-water mark, the fullest they get after snowmelt, and most of the reservoirs we track are already below their normal July level. The Colorado River headwaters are the weakest spot: Blue Mesa ~39%, Green Mountain ~32%, Lake Granby ~68%, all near five-year lows after one of the lowest snowpacks on record. As the source of the Colorado, Rio Grande, Arkansas and South Platte, a short year here becomes the downstream West's shortage a year later.
New Mexico Reservoir Levels, July 2026: The Driest State, With Elephant Butte Near Empty
New Mexico is the driest reservoir state we track, about 27% full in early July 2026, with 13 of 16 reservoirs below their normal July level. Elephant Butte, the state's largest reservoir, sits at roughly 3.6% on a Rio Grande system running near empty — Caballo ~9%, Heron ~13% — while the San Juan basin in the northwest holds up far better, with Navajo Reservoir near 57%. In a state this dry, which river a reservoir sits on decides almost everything.
Utah Reservoir Levels, July 2026: The 32% Headline Is Really Just Lake Powell
Utah's reservoirs read about 32% full in early July 2026 — but that number is almost entirely Lake Powell, the Colorado River giant at ~22% that holds nearly four-fifths of the state's tracked capacity. Strip Powell out and the rest of Utah averages ~71%, yet 22 of the 27 reservoirs we track are below their normal July level after a weak snow year. Two stories at once: one near-empty giant on the Colorado, and a whole state of snow-fed reservoirs quietly running dry.
India Reservoir Levels, July 2026: 24% Full at the Monsoon Floor
India's monitored reservoirs are holding about 24% of capacity (roughly 53 km³) in early July 2026 — essentially flat on June and still at the annual pre-monsoon floor. The big northern and central reservoirs that carry the national number kept emptying through late June: Indira Sagar, the country's largest, is down near 15%, Hirakud on the Mahanadi is at 15%, and Rihand and Bhakra each fell 10–15 points in six weeks. About 120 of the ~290 reservoirs with a live reading are below 20% full. July is the month the monsoon is supposed to flip these dams from drawdown to refill — the trajectory, not the level, is the signal.
Arizona Reservoir Levels, July 2026: Roosevelt Lake Falls to 39%
Arizona's reservoirs averaged about 64% full in July 2026, but the number is propped up by reservoirs kept near full by design — Lake Mohave (~105%), Lake Havasu (~89%) and the small Salt River hydro lakes (92–96%). The state's real storage is draining: Roosevelt Lake, the largest reservoir wholly inside Arizona, fell to 39% from 90% two years earlier, San Carlos is empty, and the Colorado River bank in Lake Mead (~26%) and Lake Powell (~22%) sits near its long-term lows.
Texas Reservoir Levels, July 2026: Full in the North, Emptying in the South
Texas enters July 2026 about two-thirds full statewide — but that average hides two states. North and East Texas reservoirs are near capacity (Lake Texoma ~103%, Lake Conroe ~100%), while South and West Texas are in a multi-year drought: Choke Canyon is down to ~8% and has fallen every July for five years, and the Corpus Christi supply is critically low. Full lakes 300 miles north can't help — Texas has no grid to move the water.
Is Your Tap Water "Good"? The Taste Formula Says the Purest Isn't Best
There is a real, published taste formula for tap water — and by it, the purest water is not the best. Devesa and Dietrich (2018) found drinking-water taste peaks in a sweet spot of roughly 200–400 mg/L of total dissolved solids and turns flat below ~100 mg/L. Run six US cities through it and the result inverts the popular consensus: famously soft, beloved New York (73 mg/L) and Boston (96 mg/L) sit below the taste optimum, while mineral-rich Los Angeles (252) and Washington, D.C. (201) land squarely in the sweet spot. One blunt caveat: "good" here means taste, not safety — all six meet US EPA standards, and below-optimum doesn't mean bad.
How We Get Our Data, Part 2: The United States — Open Everywhere, Together Nowhere
India was a locked door; the United States is the opposite problem. Almost nothing is hidden, but there is no single source — the data is scattered across half a dozen federal agencies, and for some states the reservoirs that matter most appear in none of them. Run the federal stack over New York and you get one empty flood-control dam, while the Catskill and Delaware reservoirs that supply New York City — about 88% full — sit in no federal feed at all. Here is the honest version of how we assembled 517 US reservoirs across 36 states.
How We Get Our Data, Part 1: India — the Hardest Country We Track
Reservoirs.earth grades countries on how openly they publish reservoir data, so we're publishing our own process too. Part 1 is India — the hardest country we track: a national bulletin page frozen for over a year, a live system locked behind encryption and a login, government domains that won't resolve from abroad, and a separate scraper for half a dozen state water portals. We run the project from Spain, and India's servers don't answer to a Spanish address.
India Reservoir Levels, June 2026: 27% Full and Waiting on the Monsoon
India's monitored reservoirs sit at about 27% of usable capacity (about 54 km3) as of 25 June 2026 — the seasonal pre-monsoon floor. About 110 of the reservoirs we track are below 20% full. The driest states are Karnataka (~10%), Odisha (~14%) and Telangana (~15%); the lowest big reservoirs are Tungabhadra and Krishnaraja Sagar on the Krishna and Cauvery in the south.
Mettur Dam Water Level, June 2026: 44% Full and Running Below Normal
Mettur Dam (Stanley Reservoir) is about 43.9% full as of 26 June 2026, holding 1,163 MCM of its 2,647 MCM capacity. That is roughly 12 points below the typical June fill of 56%, leaving the reservoir near its usual April low. Mettur is sitting at its pre-monsoon floor, and its refill now hinges on the southwest monsoon over the Cauvery catchment in Karnataka and on upstream releases.
California Reservoir Levels, June 2026: Above Average and Far Above the Drought Years
California enters summer 2026 with reservoirs about 82% of capacity — roughly 107% of the historical average and far above the 2015 and 2021 droughts, when these dams sat 35-51% full. A strong water-supply position. The honest caveat: a full reservoir measures water, not the fire season, which runs on weather and stays unpredictable.
Brazil Reservoir Levels, June 2026: Full Reservoirs, Low Power Bills
In Brazil the reservoir level is the electricity price: hydropower is about half of generation, so full reservoirs mean cheap power and a low tariff flag, while low ones fire up expensive thermal plants. As of mid-June 2026 the big hydro reservoirs are mostly full to comfortable after a wet end to 2025 — the North and Northeast near full (Tucuruí ~95%), the Southeast/Centre-West comfortable, the South the laggard. A normal-to-good June, the opposite of the 2021 water crisis.
US Reservoir Levels vs Normal: Where Drought Risk Is Building, June 2026
US reservoirs are about 66% full in June 2026 — only around 4 points below the typical June level. But drought risk is regional and counterintuitive: Lake Mead is near its (chronically low) normal, while the real declines are upstream and north — Idaho's Snake River, the Upper Colorado Rockies, and a dry Mississippi. California, the state everyone associates with drought, is above normal. A look at which states are below their usual June levels, and why low isn't the same as drought risk.
Australia Reservoir Levels, June 2026: Full Coast, Dry Inland Southeast
As of mid-June 2026, Australia's reservoirs are about 59% full nationally — close to normal for early winter, but hiding a sharp split. The coast and tropical north are full (Sydney's Warragamba near 97%, Lake Argyle brimming), while the inland Murray-Darling is well below average: Lake Menindee near 9%, Hume and Burrendong around 30%. Tasmania reads low but that is hydro operation, not drought. The June edition of a monthly check-in on the major water economies.
US Reservoir Levels: The Driest States and the Reservoirs to Watch in 2026
Across the ~600 major reservoirs we track in 37 states, US storage sits at about 65% of capacity in mid-2026 — but the average hides a sharp split. The arid Southwest is near-empty while the northern Plains and California are close to full. Here are the driest states (Nevada, New Mexico, Utah), the most depleted reservoirs (Elephant Butte, Lake Powell, Lake Mead), where the data comes from, and why a low percentage doesn't always mean drought.
South Africa Dam Levels: National and Provincial Water Storage, Explained
South Africa's dam levels are published weekly by the Department of Water and Sanitation (DWS), covering about 218 dams that hold more than 90% of national storage. Here's where the national figure comes from, how it splits across the nine provinces, and where to track any single dam — from Gariep and the Vaal to Theewaterskloof and Midmar.
Why reservoir data must be public: the case for water transparency
Governments measure their reservoir storage to the cubic metre, around the clock — transparency only decides whether the public sees the number too. Open water data keeps the state from being the only one holding it, earns international credibility, tells you which opportunities are real, and answers whether you need to build more reservoirs at all.
The perfect score: what it would take for a country to reach 100/100 on the RTI
No country scores 100 on the Reservoir Transparency Index — Norway leads at 89.3. A perfect score isn't about having the most water; it's seven concrete things, and every one of them is already done by some country today.
Strategic withholding: when reservoir data becomes a diplomatic weapon
Egypt hides Aswan storage from public view. Ethiopia keeps GERD opaque. Kyrgyzstan actively pulled Toktogul data in 2025. The pattern is consistent: upstream-downstream tension produces deliberate opacity.
How we evaluated 194 countries (and what we got wrong the first time)
Behind the scenes: parallel research agents, denominators that needed three revisions, and the methodology bug that mis-graded India for two months. A transparent post-mortem.