The base data source for catchments and river network is topography, generally a dem. These can be fixed at say 30 m resolution, or mixed, say by the addition of lidar where it is available. Analysis of the dem shows where water will flow to. Places where water flow directions are diverging are catchment divides and convergences eventiuallyu accumulate to make a big enough area to say "here is a stream". This does not mean there is water in it, simply that a threshold area drains to this point. Thus rivers and catchments both derive from the topography.

Names are attached to every section of a given river and the only distinction is whether you can see them at a particular level of display. Apart from language and cultural issues I do not know any reason why a reach (river between two confluences) would have more than one name.

Shankar could tell us about data models. I suspect the REC was well informed about this from the outset. The only thing it does not have is a network numbering system and while these exist, a case is yet to be made for yet a nother numbering method. We have had five already to my knowledge (SCRCC, Wood, Hutchinson, Barnett, WONI) and the first has been most use to date. However a digital network does give a new opportunity here.

Roddy
... from my mobile.

Catchments?

Please excuse my ignorance - but is a catchment defined purely in respect
of a collection of reaches,  or by some other geographical feature such as
topography?

If the former then catchments would be a derived data set from the river
net.

The mapping of names to river features is not simple either as any given
stretch of water may possess several names depending on the viewpoint or
scale.

I would expect that some bigger countries may have already established a
good data model for a river network and that a review of these would be
useful.

A.


On 18/12/12 4:55 PM, "Dave West"  wrote:

>I agree with Andrew, practical considerations given: the chances of
>getting funding, wide buy in and wide use of "Rivernet" would be
>maximised by getting the geographic features (linework ) right. I have
>had seperate email exchanges with Auckland Council and Canterbury people
>about fixes for linework they have highlighted using their higher
>resolution LIDAR mapping etc. Get the backbone right so we hang the
>attributes in the right place as we develop them.
>
>Note I would add that Iain Gover X DOC now Ngai Tahu GIS analyst has done
>a fairly comprehensive naming of the REC reaches for DOC that is better
>than I have seen from NIWA so we could add that to the pot. Iain has also
>highlighted some improvements that might be possible.
>
>What about catchment polygon features? Part of this or another
>"Catchmentnet" ??
>-----------------------------------------
>Full text of this topic in RiverNet:
>http://dataversity.org.nz/r/topic/77HdWdebaeCl4KZEYuAqby
>
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another 02c worth...

Rivernet does not exist in a vacuum. What is the scope of what the parties here see for rivernet?

I do see merit in what Andrew suggests - get all that we can of the 
existing river network data up in some quick & reusable way for 
users to share, but I suggest we need to consider the 
broader picture. Feel free to disagree :-)

Jochen identifies a lack of longer term planning, governance structures & standards enabling "national consistency", as the real problems we should be facing up to. Just taking some existing data, sticking them in a database & delivering via a web service or portal is merely continuing the previous shortsighted approach he decries.

I think diving straight in to a simplistic "just manage existing data" solution is applying a bandaid. If done early on, it should only be done as part of a well governed & managed process considering the longer term, seeking to ensure rivernet becomes an integrated part of a national framework dealing with all NZ freshwater related (& environmental) data. 


Brent Wood

I agree with Andrew, practical considerations given: the chances of getting funding, wide buy in and wide use of "Rivernet" would be maximised by getting the geographic features (linework ) right. I have had seperate email exchanges with Auckland Council and Canterbury people about fixes for linework they have highlighted using their higher resolution LIDAR mapping etc. Get the backbone right so we hang the attributes in the right place as we develop them.

Note I would add that Iain Gover X DOC now Ngai Tahu GIS analyst has done a fairly comprehensive naming of the REC reaches for DOC that is better than I have seen from NIWA so we could add that to the pot. Iain has also highlighted some improvements that might be possible.

What about catchment polygon features? Part of this or another "Catchmentnet" ??

On 18/12/12 1:10 PM, "Jochen Schmidt"  wrote:

>Many scientists, managers, consultants, and citizens are using
>information related to rivers, lakes, and catchments in New Zealand. For
>example, the location (toplogogy) in a river network is critical to
>understand stream health and water quality in an environmental context.
>Therefore environmental monitoring, management, and science have used and
>use references to river network locations.
>
>However, there is no officially accepted and well maintained national
>database and consistent national system to enable that! Information often
>is spread across agencies and individuals.
>
>What we have includes:
>- a list of catchments names and numbers from 1956 which is widely used
>(see e.g. https://www.niwa.co.nz/freshwater-and-estuaries/nzffd) but not
>curated, maintained and geospatially referenced.
>- a REC river network created in 2004, which is now widely used and many
>parameters have been attached to that network.
>- recently NIWA created through TFBIS funding a new river network
>("REC2") (more information soon on this blog).
>- more???
>
>All of those approaches have created temporary solutions, with the main
>drawback that no maintenance of those datasets, and development of tools
>and processes to ensure national usage and therefore national consistency.
>
>I hypothesize that New Zealand needs a "national river network
>(rivernet)" which includes: well maintained reference datasets,
>appropriate data infrastructures, appropriate services and tools around
>the data to enable users and to ensure information consistency. Most
>importantly New Zealand needs a community and a governance framework (in
>its widest sense) (and of course resources) to keep all that alive. I
>have created this blog with the vision to work towards a community-based
>solution for that need.
>
>Regards, Jochen
>
>
>-----------------------------------------
>Full text of this topic in RiverNet:
>http://dataversity.org.nz/r/topic/3EZEubm3Kovwtr6pi9tkSY
>
>To leave RiverNet, email
>mailto:rivernet@dataversity.org.nz?Subject=unsubscribe
>
>Start your own free groups and site with
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>
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Diving straight in.

I'll suggest that we should enable the separation of the geographic
features and their attributes so that the the river network and catchments
resources are as minimal and simple as possible.  E.g ID, geometry, name
etc.   We can then have multiple attribute datasets that cross reference
to the ids. E.g. River Environment,  Hydro characteristics, etc.

Andrew


On 18/12/12 1:10 PM, "Jochen Schmidt"  wrote:

>Many scientists, managers, consultants, and citizens are using
>information related to rivers, lakes, and catchments in New Zealand. For
>example, the location (toplogogy) in a river network is critical to
>understand stream health and water quality in an environmental context.
>Therefore environmental monitoring, management, and science have used and
>use references to river network locations.
>
>However, there is no officially accepted and well maintained national
>database and consistent national system to enable that! Information often
>is spread across agencies and individuals.
>
>What we have includes:
>- a list of catchments names and numbers from 1956 which is widely used
>(see e.g. https://www.niwa.co.nz/freshwater-and-estuaries/nzffd) but not
>curated, maintained and geospatially referenced.
>- a REC river network created in 2004, which is now widely used and many
>parameters have been attached to that network.
>- recently NIWA created through TFBIS funding a new river network
>("REC2") (more information soon on this blog).
>- more???
>
>All of those approaches have created temporary solutions, with the main
>drawback that no maintenance of those datasets, and development of tools
>and processes to ensure national usage and therefore national consistency.
>
>I hypothesize that New Zealand needs a "national river network
>(rivernet)" which includes: well maintained reference datasets,
>appropriate data infrastructures, appropriate services and tools around
>the data to enable users and to ensure information consistency. Most
>importantly New Zealand needs a community and a governance framework (in
>its widest sense) (and of course resources) to keep all that alive. I
>have created this blog with the vision to work towards a community-based
>solution for that need.
>
>Regards, Jochen
>
>
>-----------------------------------------
>Full text of this topic in RiverNet:
>http://dataversity.org.nz/r/topic/3EZEubm3Kovwtr6pi9tkSY
>
>To leave RiverNet, email
>mailto:rivernet@dataversity.org.nz?Subject=unsubscribe
>
>Start your own free groups and site with
>OnlineGroups.Net http://onlinegroups.net
>
>Host your own online groups site with
>GroupServer http://groupserver.org