pynhd.network_tools

Access NLDI and WaterData databases.

Module Contents

class pynhd.network_tools.NHDTools(flowlines)

Prepare NHDPlus data for downstream analysis.

Notes

Some of these tools are ported from nhdplusTools.

Parameters:

flowlines (geopandas.GeoDataFrame) – NHDPlus flowlines with at least the following columns: comid, lengthkm, ftype, terminalfl, fromnode, tonode, totdasqkm, startflag, streamorde, streamcalc, terminalpa, pathlength, divergence, hydroseq, and levelpathi.

add_tocomid()

Find the downstream comid(s) of each comid in NHDPlus flowline database.

Notes

This functions requires the following columns:

comid, terminalpa, fromnode, tonode

static check_requirements(reqs, cols)

Check for all the required data.

Parameters:

• reqs (iterable) – A list of required data names (str)

• cols (list) – A list of variable names (str)

clean_flowlines(use_enhd_attrs, terminal2nan)

Clean up flowlines.

Parameters:

• use_enhd_attrs (bool) – Use attributes from the ENHD database.

• terminal2nan (bool) – Convert terminal flowlines to NaN.

remove_isolated()

Remove isolated flowlines.

remove_tinynetworks(min_path_size, min_path_length, min_network_size)

Remove small paths in NHDPlus flowline database.

Notes

This functions requires the following columns: levelpathi, hydroseq, totdasqkm, terminalfl, startflag, pathlength, and terminalpa.

Parameters:

• min_network_size (float) – Minimum size of drainage network in sqkm.

• min_path_length (float) – Minimum length of terminal level path of a network in km.

• min_path_size (float) – Minimum size of outlet level path of a drainage basin in km. Drainage basins with an outlet drainage area smaller than this value will be removed.

to_linestring()

Convert flowlines to shapely LineString objects.

pynhd.network_tools.enhd_flowlines_nx()

Get a networkx.DiGraph of the entire NHD flowlines.

Changed in version 0.16.2: The function now replaces all 0 values in the tocomid column of ENHD with the negative of their corresponding comid values. This ensures all sinks are unique and treated accordingly for topological sorting and other network analysis. The difference are in the returned label2comid dictionary and onnetwork_sorted which will contain the negative values for the sinks.

Notes

The graph is directed and has the all the attributes of the flowlines in ENHD. Note that COMIDs are based on the 2020 snapshot of the NHDPlusV2.1.

Returns:

• graph (networkx.DiGraph) – The generated directed graph

• label2comid (dict) – A mapping of COMIDs to the node IDs in the graph

• onnetwork_sorted (list) – A topologically sorted list of the COMIDs.

Return type:

tuple[networkx.DiGraph, dict[int, int], list[int]]

pynhd.network_tools.flowline_resample(flw, spacing, id_col='comid', smoothing=None)

Resample a flowline based on a given spacing.

Parameters:

• flw (geopandas.GeoDataFrame) – A dataframe with geometry and id_col columns and CRS attribute. The flowlines should be able to merged to a single LineString. Otherwise, you should use the network_resample() function.

• spacing (float) – Spacing between the sample points in meters.

• id_col (str, optional) – Name of the flowlines column containing IDs, defaults to comid.

• smoothing (float or None, optional) – Smoothing factor is used for determining the number of knots. This arg controls the tradeoff between closeness and smoothness of fit. Larger smoothing means more smoothing while smaller values of smoothing indicates less smoothing. If None (default), smoothing is done with all points.

Returns:

geopandas.GeoDataFrame – Resampled flowline.

Return type:

geopandas.GeoDataFrame

pynhd.network_tools.flowline_xsection(flw, distance, width, id_col='comid', smoothing=None)

Get cross-section of a river network at a given spacing.

Parameters:

• flw (geopandas.GeoDataFrame) – A dataframe with geometry and, id_col, and levelpathi columns and a projected CRS attribute.

• distance (float) – The distance between two consecutive cross-sections.

• width (float) – The width of the cross-section.

• id_col (str, optional) – Name of the flowlines column containing IDs, defaults to comid.

• smoothing (float or None, optional) – Smoothing factor is used for determining the number of knots. This arg controls the tradeoff between closeness and smoothness of fit. Larger smoothing means more smoothing while smaller values of smoothing indicates less smoothing. If None (default), smoothing is done with all points.

Returns:

geopandas.GeoDataFrame – A dataframe with two columns: geometry and comid. The geometry column contains the cross-section of the river network and the comid column contains the corresponding comid from the input dataframe. Note that each comid can have multiple cross-sections depending on the given spacing distance.

Return type:

geopandas.GeoDataFrame

pynhd.network_tools.mainstem_huc12_nx()

Get a networkx.DiGraph of the entire mainstem HUC12s.

Notes

The directed graph is generated from the nhdplusv2wbd.csv file with all attributes that can be found in Mainstem. Note that HUC12s are based on the 2020 snapshot of the NHDPlusV2.1.

Returns:

• networkx.DiGraph – The mainstem as a networkx.DiGraph with all the attributes of the mainstems.

• dict – A mapping of the HUC12s to the node IDs in the graph.

• list – A topologically sorted list of the HUC12s which strings of length 12.

Return type:

tuple[networkx.DiGraph, dict[int, str], list[str]]

pynhd.network_tools.network_resample(flw, spacing, id_col='comid', smoothing=None)

Resample a network flowline based on a given spacing.

Parameters:

• flw (geopandas.GeoDataFrame) – A dataframe with geometry and, id_col, and levelpathi columns and a projected CRS attribute.

• spacing (float) – Target spacing between the sample points in the length unit of the flw’s CRS.

• id_col (str, optional) – Name of the flowlines column containing IDs, defaults to comid.

• smoothing (float or None, optional) – Smoothing factor is used for determining the number of knots. This arg controls the tradeoff between closeness and smoothness of fit. Larger smoothing means more smoothing while smaller values of smoothing indicates less smoothing. If None (default), smoothing is done with all points.

Returns:

geopandas.GeoDataFrame – Resampled flowlines.

Return type:

geopandas.GeoDataFrame

pynhd.network_tools.network_xsection(flw, distance, width, id_col='comid', smoothing=None)

Get cross-section of a river network at a given spacing.

Parameters:

• flw (geopandas.GeoDataFrame) – A dataframe with geometry and, id_col, and levelpathi columns and a projected CRS attribute.

• distance (float) – The distance between two consecutive cross-sections.

• width (float) – The width of the cross-section.

• id_col (str, optional) – Name of the flowlines column containing IDs, defaults to comid.

• smoothing (float or None, optional) – Smoothing factor is used for determining the number of knots. This arg controls the tradeoff between closeness and smoothness of fit. Larger smoothing means more smoothing while smaller values of smoothing indicates less smoothing. If None (default), smoothing is done with all points.

Returns:

geopandas.GeoDataFrame – A dataframe with two columns: geometry and comid. The geometry column contains the cross-section of the river network and the comid column contains the corresponding comid from the input dataframe. Note that each comid can have multiple cross-sections depending on the given spacing distance.

Return type:

geopandas.GeoDataFrame

pynhd.network_tools.nhdflw2nx(flowlines, id_col='comid', toid_col='tocomid', edge_attr=None)

Convert NHDPlus flowline database to networkx graph.

Parameters:

• flowlines (geopandas.GeoDataFrame) – NHDPlus flowlines.

• id_col (str, optional) – Name of the column containing the node ID, defaults to “comid”.

• toid_col (str, optional) – Name of the column containing the downstream node ID, defaults to “tocomid”.

• edge_attr (str, optional) – Name of the column containing the edge attributes, defaults to None. If True, all remaining columns will be used as edge attributes.

Returns:

nx.DiGraph – Networkx directed graph of the NHDPlus flowlines. Note that all elements of the toid_col are replaced with negative values of their corresponding id_cl values if they are NaN or 0. This is to ensure that the generated nodes in the graph are unique.

Return type:

networkx.DiGraph

pynhd.network_tools.nhdplus_l48(layer=None, data_dir='cache', **kwargs)

Get the entire NHDPlus dataset.

Notes

The entire NHDPlus dataset for CONUS (Lower 48) is downloaded from here. This 7.3 GB file will take a while to download, depending on your internet connection. The first time you run this function, the file will be downloaded and stored in the ./cache directory. Subsequent calls will use the cached file. Moreover, there are two additional dependencies required to read the file: pyogrio and py7zr. These dependencies can be installed using pip install pyogrio py7zr or conda install -c conda-forge pyogrio py7zr.

Parameters:

• layer (str, optional) – The layer name to be returned. Either layer should be provided or sql. Defaults to None. The available layers are:

  • Gage

  • BurnAddLine

  • BurnAddWaterbody

  • LandSea

  • Sink

  • Wall

  • Catchment

  • CatchmentSP

  • NHDArea

  • NHDWaterbody

  • HUC12

  • NHDPlusComponentVersions

  • PlusARPointEvent

  • PlusFlowAR

  • NHDFCode

  • DivFracMP

  • BurnLineEvent

  • NHDFlowline_Network

  • NHDFlowline_NonNetwork

  • GeoNetwork_Junctions

  • PlusFlow

  • N_1_Desc

  • N_1_EDesc

  • N_1_EStatus

  • N_1_ETopo

  • N_1_FloDir

  • N_1_JDesc

  • N_1_JStatus

  • N_1_JTopo

  • N_1_JTopo2

  • N_1_Props

• data_dire (str or pathlib.Pathlib.Path) – Directory to store the downloaded file and use in subsequent calls, defaults to ./cache.

• **kwargs – Keyword arguments are passed to pyogrio.read_dataframe. For more information, visit pyogrio.

Returns:

geopandas.GeoDataFrame – A dataframe with all the NHDPlus data.

Return type:

geopandas.GeoDataFrame

pynhd.network_tools.prepare_nhdplus(flowlines, min_network_size, min_path_length, min_path_size=0, purge_non_dendritic=False, remove_isolated=False, use_enhd_attrs=False, terminal2nan=True)

Clean up and fix common issues of NHDPlus MR and HR flowlines.

Ported from nhdplusTools.

Parameters:

• flowlines (geopandas.GeoDataFrame) – NHDPlus flowlines with at least the following columns: comid, lengthkm, ftype, terminalfl, fromnode, tonode, totdasqkm, startflag, streamorde, streamcalc, terminalpa, pathlength, divergence, hydroseq, levelpathi.

• min_network_size (float) – Minimum size of drainage network in sqkm

• min_path_length (float) – Minimum length of terminal level path of a network in km.

• min_path_size (float, optional) – Minimum size of outlet level path of a drainage basin in km. Drainage basins with an outlet drainage area smaller than this value will be removed. Defaults to 0.

• purge_non_dendritic (bool, optional) – Whether to remove non dendritic paths, defaults to False.

• remove_isolated (bool, optional) – Whether to remove isolated flowlines, i.e., keep only the largest connected component of the flowlines. Defaults to False.

• use_enhd_attrs (bool, optional) – Whether to replace the attributes with the ENHD attributes, defaults to False. Note that this only works for NHDPlus mid-resolution (MR) and does not work for NHDPlus high-resolution (HR). For more information, see this.

• terminal2nan (bool, optional) – Whether to replace the COMID of the terminal flowline of the network with NaN, defaults to True. If False, the terminal COMID will be set from the ENHD attributes i.e. use_enhd_attrs will be set to True which is only applicable to NHDPlus mid-resolution (MR).

Returns:

geopandas.GeoDataFrame – Cleaned up flowlines. Note that all column names are converted to lower case.

Return type:

geopandas.GeoDataFrame

pynhd.network_tools.topoogical_sort(flowlines, edge_attr=None, largest_only=False, id_col='ID', toid_col='toID')

Topological sorting of a river network.

Parameters:

• flowlines (pandas.DataFrame) – A dataframe with columns ID and toID

• edge_attr (str or list, optional) – Names of the columns in the dataframe to be used as edge attributes, defaults to None.

• largest_only (bool, optional) – Whether to return only the largest network, defaults to False.

• id_col (str, optional) – Name of the column containing the node ID, defaults to ID.

• toid_col (str, optional) – Name of the column containing the downstream node ID, defaults to toID.

Returns:

(list, dict , networkx.DiGraph) – A list of topologically sorted IDs, a dictionary with keys as IDs and values as a list of its upstream nodes, and the generated networkx.DiGraph object. Note that node IDs are associated with the input flow line IDs, but there might be some negative IDs in the output garph that are not present in the input flow line IDs. These “artificial” nodes are used to represent the graph outlet (the most downstream nodes) in the graph.

Return type:

tuple[list[numpy.int64 | pandas._libs.missing.NAType], dict[int, list[int]], networkx.DiGraph]

pynhd.network_tools.vector_accumulation(flowlines, func, attr_col, arg_cols, id_col='comid', toid_col='tocomid')

Flow accumulation using vector river network data.

Parameters:

• flowlines (pandas.DataFrame) – A dataframe containing comid, tocomid, attr_col and all the columns that ara required for passing to func.

• func (function) – The function that routes the flow in a single river segment. Positions of the arguments in the function should be as follows: func(qin, *arg_cols) qin is computed in this function and the rest are in the order of the arg_cols. For example, if arg_cols = ["slope", "roughness"] then the functions is called this way: func(qin, slope, roughness) where slope and roughness are elemental values read from the flowlines.

• attr_col (str) – The column name of the attribute being accumulated in the network. The column should contain the initial condition for the attribute for each river segment. It can be a scalar or an array (e.g., time series).

• arg_cols (list of strs) – List of the flowlines columns that contain all the required data for a routing a single river segment such as slope, length, lateral flow, etc.

• id_col (str, optional) – Name of the flowlines column containing IDs, defaults to comid

• toid_col (str, optional) – Name of the flowlines column containing toIDs, defaults to tocomid

Returns:

pandas.Series – Accumulated flow for all the nodes. The dataframe is sorted from upstream to downstream (topological sorting). Depending on the given initial condition in the attr_col, the outflow for each river segment can be a scalar or an array.

Return type:

pandas.Series