South Korea Reservoir Transparency

South Korea publishes reservoir operational data through two parallel, formally documented public APIs on the national open data portal (data.go.kr). The K-water API (dataset 15099110) covers 61 hydraulic structures — 21 multipurpose dams, 14 water-supply dams, the Nakdong River estuary weir, 3 flood-control dams, 6 adjustment reservoirs, and 16 weirs — with fields for water level (EL.m), rainfall (mm), inflow (m³/sec), total discharge (m³/sec), storage volume (million m³) and storage rate (%). A separate Korea Rural Community Corporation API (dataset 15099919, endpoint apis.data.go.kr/B552149/reserviorWaterLevel) exposes water level and storage rate for the agricultural reservoirs directly managed by KRC. WAMIS (wamis.go.kr/ENG) provides bilingual hydrological dam data including storage-elevation relationships and historic water levels. The KMA hydro portal (hydro.kma.go.kr) additionally publishes real-time dam storage rates, and static specifications for 34 K-water dams are freely downloadable from data.go.kr without registration. The Mulmoa national integration platform (mulmoa.go.kr) launched April 2025 already consolidates 36 information types from nine previously fragmented water systems under the Ministry of Environment.

Two distinct documented REST APIs are publicly registered on Korea's national open data portal. The K-water hydrological operation endpoint (apis.data.go.kr/B500001/dam/sluicePresentCondition/hourlist) returns XML and JSON for dam water level, inflow, outflow, storage volume and storage rate at 10-minute, hourly and daily granularities. The KRC agricultural reservoir endpoint (apis.data.go.kr/B552149/reserviorWaterLevel) provides reservoir water level and storage rate, with a development quota of 10,000 daily requests expandable on use-case registration. Both require free registration on data.go.kr to obtain an API key — a one-time step, not an institutional approval barrier. K-water additionally runs opendata.kwater.or.kr (412+ datasets) with an API guide. WAMIS provides web query interfaces but no formally documented public REST endpoint at the data dictionary level; a community-maintained tutorial demonstrates that a WAMIS OpenAPI exists in practice. The score is held below 85 because all API parameter documentation, sample requests, and dataset descriptions are Korean-only, and the en.data.go.kr surface is a machine translation that omits much of the technical detail.

Conservative estimate — denominator includes the long tail of medium-sized agricultural reservoirs managed by local governments outside KRC's API coverage (~14,000 of South Korea's 17,643 agricultural reservoirs are managed by municipalities rather than KRC and are not in the RAWRIS API), plus small private/industrial impoundments. Methodology v1.3.0 (capacity-weighted). Covered capacity through the K-water API (61 strategic hydraulic structures, ~12,000 hm³) plus the KRC RAWRIS API (KRC-directly-managed agricultural reservoirs) totals approximately 12,000 hm³. A realistic national denominator including the local-government agricultural reservoir tail reaches approximately 13,600 hm³. Score = round(100 × 12,000 / 13,600) = 88. The strategically significant reservoir storage is virtually all publicly accessible through one of the two formally documented APIs; the conservative discount reflects the systematic exclusion of the local-government agricultural reservoir tail.

The K-water hydrological operation API on data.go.kr explicitly covers January 2006 to present (approximately 20 years), with retention periods varying by location. WAMIS has collected hydrological data since the late 1990s, with some stations starting records in 1998. Major dams were commissioned in the 1970s–1980s (Soyang 1973, Chungju 1985), and digital records at those facilities predate the centralised WAMIS archive. KRC began installing automatic water level gauges in agricultural reservoirs and canals in 2010, so the RAWRIS digital archive depth is shorter — roughly 15 years for the instrumented subset. UNESCO IHP-WINS mirrors WAMIS hydrometeorological data for broader academic access. A 20-year publicly accessible API record on the K-water side is substantial, but comprehensive digital archives stretching to dam commissioning dates in the 1970s are not consistently available through a single public portal, and the agricultural reservoir series is shallower.

K-water data is published at 10-minute intervals, hourly, and daily through the data.go.kr API. The KMA hydro portal (hydro.kma.go.kr) publishes real-time dam storage rates. WAMIS provides near-real-time dam hydrological data. The KRC RAWRIS API delivers reservoir water level updates from automatic gauges. This places South Korea among the highest tiers globally for update frequency of dam storage data — comparable to Taiwan's hourly tier and ahead of most national systems.

K-water publishes full technical specifications for all major dams on its English-language website, including height, length, watershed area, normal water level, planned flood level, permanent pool level, and total storage capacity. The storage rate (저수율) is explicitly defined in API metadata as the ratio of current storage volume to total storage capacity based on planned flood level. Elevation measurements use the standard EL.m reference system. The K-water dam specifications dataset on data.go.kr provides 13 structured fields per dam, and a parallel KRC facility specifications dataset (15044339) covers agricultural reservoir physical parameters. The Mulmoa platform (launched April 2025) integrates nine previously fragmented water information systems and is on track to reach 71 information types by H1 2026 and 278 by 2028. Minor deductions apply because full water level–storage volume relationship curves are not directly downloadable in a standardised format from a single public endpoint, and unified measurement-standard documentation in English remains incomplete.

WAMIS provides a genuine English-language interface at wamis.go.kr/ENG/ with English-labelled sections for dam hydrological data, water level/storage relations, and discharge data. K-water's main corporate site has a complete English version (kwater.or.kr/eng/) with dam specifications. The data.go.kr portal exposes an English surface (data.go.kr/en) where both the K-water dam API and the KRC reservoir API are discoverable with English titles and basic descriptions. However, the primary data portals — opendata.kwater.or.kr (412+ datasets) and the detailed API documentation pages on data.go.kr — are predominantly in Korean. API parameter documentation, dataset descriptions, sample requests and the K-water open data guide are Korean-only. The KMA hydro portal, RAWRIS web interface and Mulmoa are Korean-only. International researchers can locate API endpoints through English-language paths but encounter Korean documentation at the critical technical detail level. The score sits notably below Taiwan (82) because Taiwan's API field identifiers are English and a Swagger UI is published in English; Korea's field semantics require translation from Korean.