Earliest Dam Year

First load the network, and attributes

network load_file("data/ohio-river/ohio.network")
network gis_load_attrs("data/ohio-river/nid-uniq.gpkg", "nidId")

node.is_usgs = NAME match "^[0-9]+";
node.is_dam = !is_usgs;
network count(nodes.is_usgs)
network count(nodes.is_dam)

Results:

1806
4181

Counting the upstream dams again,

node<inp>.ndam = int(is_dam) + sum(inputs.ndam);
node.no_dam_us = ndam == 0;
network count(nodes.no_dam_us & nodes.is_usgs)
network count(nodes.no_dam_us & nodes.is_usgs) / count(nodes.is_usgs)

Results:

605
0.33499446290143964

We can see 33% of the USGS gages do not have dams upstream.

And for those that do, let’s look at the construction year,

env.max_year = 9999; # todo test it with nan
node.dam_year = int(get_attr("yearCompleted", env.max_year));

node<inp>.dam_aff_yr = min_num(inputs.dam_aff_yr, dam_year);
node<inp>.dam_affected = dam_aff_yr < env.max_year;

network count(nodes.dam_affected & nodes.is_usgs)
network count(!nodes.no_dam_us & nodes.is_usgs)
network count(nodes.dam_affected & nodes.is_usgs) / count(!nodes.no_dam_us & nodes.is_usgs)

Results:

1152
1201
0.9592006661115737

This shows we have the construction year for 95% of the USGS gages that were constructed after at least one upstream dams.