The EPA’s current river network layer, RivNetRoutes, has key information embedded within it, such as connections between tributaries and rivers which we need for sediment and flow modelling, and the river waterbody delineations.
The OSI has recently generated a more spatially accurate PRIME2 dataset which includes datasets pertaining to waters. It does not however, have all the attributes and capability that is required for detailed environmental modelling and assessment, in that it is not a connected network.
Several EPA projects have already used the OSI PRIME2 dataset (for example, the national landcover map and the MQI-Ireland Hydromorphology tool), establishing its importance for environmental assessments.
This project is to develop a connected river network based on the Prime2 data. A pilot project in the Suir catchment has successfully developed and tested a more spatially accurate and near-fully connected digital model of the water network in GIS. Consultants completed this work in 2022 and have developed a methodology to generate a more precise and accurate representation of our rivers using the OSI PRIME2 dataset.
The national rollout of the Connected Waterline through this project will greatly enhance the data modelling and analysis capabilities of the EPA. There will be significant benefits for example, in combining the updated waterline, land cover maps and the MQI database to carry out integrated catchment assessments. The connected network will also be of value to other key external stakeholders (for example, OPW, IFI and LAWPRO).
A bespoke on-line GIS editing portal and underlying geodatabase was developed to support the pilot. This bespoke editing portal was designed to maximise automation of the steps required to connect the network, while facilitating hydrological specialist inputs where required. It is envisaged that this portal will be used to complete the national rollout in the remaining 45 catchments.
Connected Waterline – Lots
Additional contractor resources are now being sought to roll out the Waterline Pilot project nationally for the remaining 45 catchments. The work is being divided into two Lots:
Connected Waterline Lot 1: Manage, develop and maintain the online GIS editing portal
A contractor resource is now being sought to manage, develop and maintain the on-line editing portal which contains the required tools to fix the river connection issues encountered during the national roll out of the Waterline Pilot project. The resource will develop additional custom tools for carrying out the work in hydrogeological settings not covered in the pilot, for example making routing connections where there are gaps in the PRIME2 data and through lakes.
The tool will be used by the successful tenderers of Lot 2 who will be rolling out the process nationally, the Catchments Unit team members supervising the project, and in time potentially also members of other public bodies (eg LAWPRO, IFI,Rivers Trusts) who may carry out additional field validation.
Detailed background
RivNetRoutes (https://data.gov.ie/dataset/river-network-routes) is the currently used river network in the EPA since 2005 and is also widely used across many other sectors in Ireland. This is a national fully connected routable river network. River geometries were originally generated based on the OSi 1:50,000 raster mapping and have been updated over time as new information has arisen from local surveys. The associated attribute data comes from a variety of sources, e.g., waterbody codes from the individual waterbody datasets. This layer contains an integrated flow network that includes known flow connections through rivers, lakes, estuaries (transitional waters) and groundwater aquifers. In places where the network is depicted flowing through lakes, estuaries or through underground channels, the flow channels are schematic only, and do not represent the precise location of these flow channels.
During 2014, Ordnance Survey Ireland (OSi), the national mapping agency, realised a national centralised spatial database known as PRIME2. Within PRIME2, water objects describe all water bodies currently captured by OSi. These include flowing and non-flowing, natural, and man-made water bodies, which include River, Stream, Lake, Pond, Drain and Reservoir. Full details of the data tables and terminologies used within PRIME2 can be found at: https://osi.ie/wp-content/uploads/2015/04/Prime2-V-2.pdf. For ease of reference a summary of the key terms and tables referred to in this document is provided below.
| WATER_LINE | Polylines within PRIME2 which represent river object centrelines |
| WATER_SINGLE_STREAM_LINE | Polylines within PRIME2 which represent smaller water feature centrelines (e.g. streams/drains) |
| WATER_POLY | Every piece of Ireland has a polygon type assigned to it e.g. ways (roads), vegetation, artificial or exposed areas. WATER_POLY objects represent the spatial extents of each water object (i.e. a river or lake). |
| WATER_PNT | Points located at the start and end of water objects which contain data such as Z-order etc. and which are linked by GUID’s. |
| Z-Order | The Z-Order property can be specified for each classified object to indicate the vertical order of the cross-over objects. This allows for identification of features that overlap, under/over ground, such as a river and road etc. |
| GUID | All features within PRIME2 have a unique code (GUID), which stays with that objects for its life cycle |
The EPA recently developed a hydromorphological condition assessment tool, called MQI-Ireland, which was based on the OSI PRIME2 datasets (version Q4 2018). The main reason PRIME2 was decided upon was due to the accurate free flowing sinuosity of the WATER_LINE dataset within it. The far greater level of accuracy (previously limited to 1:50,000 scale) was vital for carrying out the hydromorphological assessments required (e.g. sinuosity). During project scoping, a comparison between PRIME2 WATER_LINE and RivNetRoutes was performed, which highlighted stark differences in terms of both accuracy and sinuosity. The dis-connectivity of the water line features also caused significant issues and resulted in manual assessments having to be carried in for some aspects of the project. An assessment was carried out on behalf of the EPA to summarise the key issues relevant to EPA work programmes with the PRIME2 datasets as part of the post-production project work.
The most significant issues for EPA encountered with the PRIME2 datasets are listed below:
- Not a fully connected network:
- Large gaps exist
- Possible incorporation of closed loops
- Missing water lines where WFD water bodies are known to be present and vice-versa
- No concept of stream order or source/sink (not routable)
- Mis-representation of some WATER_LINE and WATER_POLY features
- Difference between WATER_POLY and the actual spatial extents of the water features (i.e. what is observable on OSi DigitalGlobe basemap etc.)
- Discrepancies within the WATER_PNT classifications and their relationship with the WATER_LINE and WATER_POLY features
- Discrepancies/errors in the Z order values (i.e. distinguishing where rivers pass beneath or above other PRIME2 objects such as roads)
The Suir Pilot
Overview
The EPA Catchments Unit competed the Suir pilot in 2022, with contractor support developing automated and manual processes to create a fully connected river network, which included the generation of an associated geometric network.
All codes/scripts/tools developed to produce each of these outputs have been provided to the EPA and will be available to the wining tenderer to enable the rollout nationally.
Suir Pilot Project Description
The primary goal of this pilot project was to create a fully connected river network for a pilot WFD Ireland Catchment which included the generation of an associated geometric network – both based on PRIME2. A semi-automated process to capture the steps involved in creating these datasets for the pilot was a key output which will allow a subsequent national roll-out. A number of intermediate datasets were required to produce the connected river network and geometric network, and these will be available to the winning tenderer for the national rollout.
The following summarises the key deliverables:
- Fully connected and traceable water line network matching existing WFD waterbodies (including flow direction) to the PRIME2 “WATER_LINE” and “WATER_SINGLE_STREAM_LINE” tables with digitisation to infill gaps where appropriate within the entire catchment (including the removal of all closed loops).
- Fully connected water line feature class representing water features outside of WFD waterbodies as represented in the PRIME2 “WATER_LINE” and “WATER_SINGLE_STREAM_LINE” tables for the entire catchment. These water lines have been snapped to the WFD PRIME2 water line network derived at (1) above at their sink/outlet.
- Complete feature class of “WATER_PTS” for the catchment which has had all attribute data corrected and which are snapped to “WATER_LINE” and “WATER_SINGLE_STREAM_LINE” start/end points. All attribute information corrected and populated.
- Complete feature class of “WATER_POLY” polygons for the catchment which have been corrected to match spatial extents from aerial imagery or other data sources where errors are identified. All attribute information corrected and populated to ensure consistency.
- Generation of a geometric network combining the water line and water point information produced above (similar to existing EPA geometric networks). For reference, our geometric networks database is downloadable from https://gis.epa.ie/GetData/Download (Water Section -> Rivers and Lakes -> OSI Geometric Network).
- A summary guide/report providing detailed step by step instructions on the methodology undertaken to complete each output listed above and all intermediate datasets.
Datasets to be made available
- PRIME2 WATER_LINE, WATER_SINGLE_STREAM_LINE, WATER_POLY, and WATER_PNT feature classes
- MQI Ireland dataset which was based on PRIME2
- EPA RivNetRoutes and corresponding geometric network
- EPA lake waterbody polygonsEPA monitoring point locations (river monitoring stations and hydrometric stations).
- 5m DEM
- All other relevant EPA datasets required shall be supplied subject to data confidentiality
All attribute information for the final output datasets shall be agreed at the outset of the project and may be modified during the course of the project as required. A sample minimum list of attributes for the connected river network (WFD waterbodies) is given in Table 1 below.
Table 1: sample minimum attribute information required for the connected river network
| reach_id | – unique id for each segment or reach within the river network |
| waterline_id | GUID of PRIME2 waterline (method to create new GUID’s for synthetic or digitised polylines will need to be confirmed with the OSi) |
| us_id | id of upstream WATER_PNT |
| ds_id | id of downstream WATER_PNT |
| order | Stream order (new orders may be required to account for retained water lines which are not WFD WBs). |
| WFD_WB_code | WB code for associated WFD WB within RivNetRoutes. |
| WFD_WB_name | WB code for associated WFD WB within RivNetRoutes. Non-WFD waterline will be moved to another feature class |
| MQI_reach_id | id code of associated MQI reach |
| length | length (km) of waterline |
| IS_Syntetic | Y/N – flag for whether the line has been added to join across lakes/karst etc. Can be expanded to two separate attributes if required |
| assc_feat | WFD_WB code or PRIME2 polygon GUID code for the lake/TraC associated with the synthetic line flagged above. Can be attributed as “karst” for karst network connections etc. |
Reach/segment generation
- First upstream segment/reach start points, and last downstream reach end points should be aligned with the start and end points of WFD water bodies respectively from RivNetRoutes to avoid reaches partially within two WFD water bodies. As noted above, the final decision on how river segments are to be determined shall be agreed at the commencement of the project. Consideration may also need to be given to segments breaking at impoundments where their existence is known or suspected.
- Segments/reaches should be based primarily on existing MQI reaches. The MQI reach dataset will be provided. Full details of the process of reach generation for MQI will be provided. The same process of reach generation will need to be followed for all new digitised waterline features outside of the existing MQI dataset (which currently covers approx. 60,000km of channel). Naming conventions for segments/reaches shall follow the procedure used in the MQI segmentation process – details of which will be provided.
Final Report and deliverables
The Final Report shall contain all findings and all procedures, codes, scripts and tools used to apply this methodology to all 46 WFD Catchment areas in Ireland.
The following digital deliverables shall also be produced at the end of the project in a single national dataset:
- Fully connected and traceable water line feature class which matches existing WFD waterbodies
- Fully connected water line feature class representing water features outside of WFD waterbodies
- Complete feature class of “WATER_PTS” which has been corrected
- Complete feature class of “WATER_POLY” polygons
- Generation of a geometric network combining the water line and water point information produced above (similar to existing EPA geometric networks)
All final and relevant intermediate datasets shall be provided in GIS format within file geodatabases and projected to the Irish Transverse Mercator (ITM) grid.
https://irl.eu-supply.com/ctm/Supplier/PublicPurchase/239224/1