Global Network of Isotopes in Rivers (GNIR)
The Global Network of Isotopes in Rivers (GNIR) for compiling isotope data on river waters, complementary to the 45 year old IAEA/WMO Global Network of Isotopes in Precipitation (GNIP), has been launched by the IAEA recently. The GNIR is aimed at an improved understanding of stream-aquifer interactions in the river plains, impacts of climate changes on river runoff, and human impacts on river discharge with the use of isotope data. Recent studies suggest that the impacts of storages, diversions and redirection of streamflow for water supply, hydropower, and irrigation might surpass the impact of recent and anticipated future climate changes on river runoff. Consequences of these effects include changes in frequency and extent of flooding, increased sediment load, altered groundwater recharge, and degradation of water quality and riparian ecosystems, often resulting in political disputes or upstream-downstream inequities.
The IAEA coordinated a research project during 2002–2006 entitled “Design criteria for a network to monitor isotope compositions of runoff in large rivers” as a preparatory activity for the operation of the GNIR. Isotope data were collected from about 20 large rivers from headwaters to outlets, providing a rationale for continuous monitoring in various types of rivers. The contribution and operation of GNIR is done on voluntary basis. Isotope and related data are compiled by the IAEA in a publicly available data repository (WISER, accessible at www.iaea.org/water), which contains data from other IAEA monitoring networks and isotope hydrology projects. The IAEA will compile data contributions from established river isotope networks and will promote monitoring of rivers in areas with limited isotope data, dominantly in tropical and arid regions.
The protocol for collection of isotope data from rivers allows freedom to participants depending upon local conditions, resources, and research needs. If a river discharges to the ocean, it should be sampled above the delta, so that entrainment of salt water is avoided. Likewise, sampling upstream rather than downstream of a confluence with a tributary is suggested. A second site at the headwaters, and another one on the middle reach would also be helpful, because the isotopic contents of headwaters often complements the isotopic composition of precipitation at a nearby GNIP station. The default grab sampling interval is monthly. Where possible, samples should be collected at gauge stations with additional information.
GNIR database contents:
|Mandatory Data||Optional Data|
|River Basin||Name, upstream area, land-use||Other relevant information on the basin|
|Sampling Site||Name, coordinates, elevation, map, photo||Closest GNIP station|
|Isotopic Data at Sampling Site||δ18O, δ2H,||3H, other isotopes|
|Other Data at Sampling Site||Discharge, electrical conductivity, temperature||Hydrochemistry|