The Hydrometric Database provides time series of water level river flow data collected from New Zealand's national river flow network (National Hydrometric Network). The database also stores related hydrological time series data such as rainfall amounts and river sediment concentrates.

New Zealand's hydrometric data collection began in the early 1900s when lake levels began to be monitored for hydro electric potential. Major rivers of regional importance were monitored regularly from the 1930s. During the international hydrological decade (1965-1974) monitoring started at over 50 of 90 representative river catchments. The representative water- level recording stations were operated primarily by the Ministry of Works and Development (later DSIR). Stations were also run by regional water boards.

By 1990 more than 500 water level recorders were operating either as part of the DSIR national network (290 stations for scientific and commercial purposes) or as part of local networks run by regional councils (for purposes such as water resource allocation or flood warning).

In 1994 a reduction in funding required NIWA (which had inherited the hydrological network from the former DSIR) to reduce the number of stations by 20 percent. Stations were classified as follows:

• long-term stations(over 40 long-term good quality stations to be retained indefinitely for monitoring long-term trends
• scientific stations (more than 150 stations were selected for specified scientific objectives such as monitoring river suspended sediment and water quality)
• commercial stations (almost 100 stations were required for commercial purposes, mainly hydro electric power generation)
• nationwide coverage stations (these were to ensure that the revised National Hydrometric Network provided nationwide coverage)

As a number of stations were selected for more than one class a total of 230 stations were selected to operate from 1994 onwards as part of the national network.

Regional councils also collect flow data. This data is contributed to the national database on a reciprocal sharing arrangement for 10 regional councils.

• Regional councils: for flood forecasting, low flow allocations.
• Hydro electric power industry: for resource consent applications.
• Irrigation industry: for resource consent applications.
• Researchers: to develop a variety of models based on the data.

• Time series data, some since 1905.
• ISO standards are used for data collection and data checking.
• Although the size of the network has been reduced from its peak in the 1990s, this was done scientifically.
• Damaged recorders are quickly replaced to ensure continuity of data.
• There are many users for the data.

• Not all users are able to use Tideda software.
• There have been cuts in funding.
• The monitoring of some sites is funded by commercial users. The ongoing funding of the monitoring at these sites once the commercial requirement has been finished can be problematic. A partnership approach helps overcome funding problems