ArkDSS Task 1, Spatial System Integration Subtask 1.1.c ...

ArkDSS Task 1, Spatial System Integration

Subtask 1.1.c, Irrigation Well Information Layer

Prepared for:

Colorado Water Conservation Board

and

Colorado Division of Water Resources

Prepared by:

HRS Water Consultants, Inc.

and

ElephantFish, LLC

FINAL

September 21, 2020

Contract No. CT2018-00578, ArkDSS Spatial System Integration Component

HRS Job No. 17-02

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Table of Contents Executive Summary ....................................................................................................................................... 2

SEO Compiled Historic Well Datasets ........................................................................................................... 4

Split Historic Well Datasets ........................................................................................................................... 5

Well to Parcel Assignment ............................................................................................................................ 6

Assign Well Attribute Data to Irrigated Parcels .......................................................................................... 11

Comments on Deliverable Limitations ........................................................................................................ 12

Final Deliverables ........................................................................................................................................ 12

State Refinements ....................................................................................................................................... 13

List of Tables

Table 1 Historic Well Datasets Table 2 Key attributes in the historic wells’ datasets Table 3 Snapshot year historic well datasets Table 4 Input and output datasets used with the ET GeoWizard’s Tool “Global Snap Points” Table 5 Excerpt of the attribute table for the irrigated parcel dataset, including joined attributes

from the historic well datasets.

List of Figures

Figure 1 General historic well information layer workflow Figure 2 Location and extent of historic wells datasets Figure 3 Historic wells inside and outside the HI Model Boundary for each snapshot year Figure 4 Original well location and snapped well location Figure 5 Flow chart displaying steps followed during the inspection phase. Figure 6 “ET_Status” of historic wells per snapshot year – snapped, manual assign, and NA

Figure 7 Example of a well that was not snapped to a parcel.

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Executive Summary This technical memorandum documents the approach, deliverables, and limitations for Subtask 1.1.c,

Irrigation Well Information Layer, prepared under Task 1, Spatial System Integration, of the Arkansas

River Decision Support System (ArkDSS).

This memorandum and the related GIS deliverables were prepared by HRS Water Consultants, Inc. (HRS)

and ElephantFish, LLC (EF). Staff from the State Engineers Office (SEO), the Colorado Water

Conservation Board (CWCB), and Division 2 staff at Colorado Division of Water Resources

(CDWR/Division 2), also assisted in completing this task.

The original objective of Subtask 1.1.c was to use Hydrobase well information to create a Geographic

Information System (GIS) coverage of irrigation well locations. The well coverage was to list irrigation

well attributes including well “start” and (if applicable) “end” dates, to indicate the period of use of the

irrigation wells in Division 2. However, per discussions with the SEO and Division 2 GIS staff, the Subtask

1.1.c scope was revised to entail assigning “historic wells” as a groundwater source to irrigated parcels

for each irrigated parcel snapshot year (1954, 1975, 1988, and 1998; see ArkDSS Task 1.3) based on a

semi-automated process in GIS. A “historic well” is a well that was not associated with an irrigated

parcel in the SEO’s 2010 irrigated parcel dataset. The historic well information1 was provided by the SEO

and Division 2 as two GIS coverages.

The general approach, displayed in Figure 1, consisted of:

The SEO and Division 2 GIS staff compiling historic well data which was delivered to HRS.

HRS reviewing and aggregating these datasets and filtering the results based each of the wells’

status (i.e., in service/not in service or does not exist) during each irrigated acreage snapshot

year (1954, 1975, 1988, and 1998).

HRS assigning the historic wells as a groundwater source to the Task 1.3 irrigated parcels (i.e.

adding the wells’ WDIDs2 to the irrigated parcels’ attribute table) for each snapshot year based

on geographic location using a semi-automated process in GIS.

The SEO and Division 2 each provided HRS with a point GIS coverage of historic wells. Division 2

provided HRS with historic wells inside the HI model area. The SEO provided HRS with wells mostly

outside of the HI model area. HRS reviewed and aggregated the two GIS coverages using spatial and

temporal filters. The spatial aggregation created two datasets – wells inside the HI model area and wells

outside the HI model area. The temporal filtering created historic well datasets for each snapshot year.

This was needed because not all wells were in service for the full period between 1954 and 1998. This

resulted in eight total datasets (inside and outside HI model datasets for the four snapshot years).

1 The historic well coverage only includes wells in service between 1954 and 1998; this does not include all wells in Division 2. Thus, the wells shown on the maps, graphs, and tables in this memorandum only encompass the historic well information layer provided by the SEO and Division 2. 2 The groundwater diversion ID (WDID) is a unique identifier for well structures in Hydrobase.

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To assign each well to an irrigated parcel, the “Global Snap Points” tool, an ArcGIS plugin by ET

Geowizards3 was used. This tool “snapped” or moved each well (GIS point) to the nearest irrigated

parcel within ¼ mile, allowing the well to be designated as a water source for the parcel. Some wells

were not within a ¼ mile of a parcel; these wells were visually inspected in GIS. A portion of these wells

were manually attributed to an existing parcel. For the remaining wells, some were linked with newly

digitized parcels and a very small number were not attributed to any parcel. While this approach has

some inherent assumptions and limitations, which are discussed below, it allows for historic wells to be

efficiently linked to nearby irrigated parcels.

The Task 1.1.c GIS deliverables were provided to the State in May 2019 and included:

Two file geodatabases containing wells inside the HI model area (HistoricWells_InsideHI.gdb)

and outside the HI model area ( HistoricWells_OutsideHI.gdb)

Each file geodatabase contained a point file for each snapshot year – 1954, 1975, 1988, and

1998 (8 total point files)

A related deliverable was the Task 1.3 file geodatabase containing the irrigated acreage for the snapshot

years (HistoricIrrigatedAcreage.gdb) with the groundwater sources linked during Task 1.1.c.

Figure 2. Task 1.1.c Memorandum layout and general historic well information layer workflow

In summary, the method used to assign historic wells to the snapshot year irrigated parcels was

primarily based on the proximity of the well to a parcel and the completion date and abandonment date

of the well. In cases where there was no proximal irrigated parcel, HRS visually inspected the area

around the well and either digitized new irrigated acreage or associated the well with a slightly more

distant parcel that could reasonably be served by the well. While this method can be inexact at the

3 ET GeoWizards is a collection of geospatial processing tools that has a seamless integration with ArcGIS Desktop.

More detailed information regarding the plugin can be found here: https://www.ian-ko.com/

https://www.ian-ko.com/

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parcel level, we believe it provides a reasonable generalized representation of the location and timeline

of historic well groundwater use in Division 2.

SEO Compiled Historic Well Datasets The SEO and Division 2 reviewed decrees, permits, correspondence, and/or field visit summaries to

compile the historic well data, which was provided to HRS. This dataset consisted of historic wells that

were likely in use between 1954 and 1998 (i.e., during the irrigated parcel dataset snapshot years). The

data were delivered as point feature classes within a file geodatabase and included the layers

Well_List_Inside_HI and Well_List_OutsideHI (Table 1). The Wells_List_Inside_HI contained only wells

within the HI model area. However, Well_List_OutsideHI contained some wells within the HI model area

in addition to the wells outside (Figure 2). The two datasets shared attribute schema and included well-

specific data such as name, decree, feature type, WDID, LocAccurac, StartNum, EndNum, and website

links (see Table 2 for a description of key table attributes).

Table 1. Historic Well Datasets

Name Geographic Location of Points

# of Well Points Compiled By Notes

Well_List_Inside_HI Inside the HI Model Boundary

418 Division 2 NA

Well_List_OutsideHI Both inside and outside the HI Model Boundary

411 SEO 38 of the 411 wells are located within the HI Model Boundary

Table 2. Key attributes in the historic wells’ datasets

Field Name Field Information

WDID Unique numeric identifier given to each well

LocAccurac Indication of the accuracy of how the well was located. (ie. GPS or spotted from section/quarters)

StartNum Year that well came into existence or first starting pumping.

EndNum Year that well was either abandoned or last pumped.

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Figure 2. Location and extent of historic wells datasets.

Split Historic Well Datasets HRS reviewed the two historic well datasets and aggregated them into eight feature classes based on two characteristics:

Spatial - whether the well was located inside or outside the HI Model boundary

Temporal - when a well was in service (i.e., began and ended pumping)

First, the wells were queried based on location to separate wells within the HI model area from wells

outside the HI model area, resulting in two datasets. Then, temporal queries were performed on both

the “Inside HI” and “Outside HI” datasets to aggregate the wells by snapshot year using the date

pumping began (StartNum) and the date pumping ended (EndNum):

o If StartNum <= 1954 and EndNum >= 1954, then include in 1954 dataset



o If StartNum <= 1998 and EndNum >=1998, then include in 1998 dataset

The number of total historic wells in each dataset is shown in Table 3 and displayed on Figure 2. There is

the largest number of historic wells in service during the 1975 snapshot and the least wells in the 1998

snapshot. It is important to note that this list contains only historic wells; present day wells are not

included. Thus, it is unlikely that there were fewer total wells in service in 1998 than in 1975. Rather,

some of the wells in service in 1998 are likely present-day wells that are not included in this memo.

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Table 3. Snapshot year historic well datasets

Name Number of Historic Wells

Well_OutsideHI_1954 236

Well_InsideHI_1954 188







Figure 3. Historic wells inside and outside the HI Model Boundary for each snapshot year

Well to Parcel Assignment After splitting the datasets, each well was assigned as a water source to an associated irrigated parcel.

Each well’s WDID was added to the attribute table for the associated irrigated parcel. For example, each

well in the Well_OutsideHI_1954 dataset was assigned to an irrigated parcel in the 1954 irrigated parcel

dataset4 (Table 4). HRS and the SEO developed an assignment approach using a semi-automated spatial

process to assign historic wells efficiently to irrigated parcels.

4 The goal was to assign all wells to irrigated parcels. Although, most wells were assigned, it was not possible to assign every well to a parcel.

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First, the ET GeoWizard’s Tool “Global Snap Points” (snap tool) was used. This tool moves and “snaps”

each point within a dataset to the closest snap layer dataset (in this case the irrigated parcel polygons).

HRS set the snap tool’s maximum distance setting to a ¼ mile and ran the tool with the input and output

datasets shown in Table 4. The snap tool’s output was a point shapefile with each point shifted to the

closest vertex of the snap layer (Figure 4). The new point shapefile’s attribute table is populated with an

“ET_Status” binary field, which can be either:

Snapped = The point was snapped to a polygon within the spatial tolerance provided, or

Original = The point was not snapped to a polygon because no polygon fell within the spatial

tolerance provided of ¼ mile.

Table 4. Input and output datasets used with the ET GeoWizard’s Tool “Global Snap Points”

Well Dataset (input) Snap Layer (input) Output Shapefile

Well_OutsideHI_1954 IrrigParcels_1954

Well_OutsideHI_1954_Snapped

Well_InsideHI_1954 Well_InsideHI_1954_Snapped










The output files were reviewed and when a well was given an ET_Status of “Snapped,” its location was

left unchanged; however, if a well was given an ET_Status of “Original,” the well location was visually

inspected using GIS (Figure 5). HRS looked for irrigated parcels nearby that could reasonably be

irrigated by the well. If an irrigated parcel was located, the well was assigned to that parcel and the

ET_Status was changed to “ManualAssign.” If a digitized irrigated parcel was not present, HRS looked

for the presence of a possibly irrigated area that was not included in the Task 1.3 irrigated acreage

coverage. If a previously not digitized irrigated area was located, it was digitized and added to the

respective irrigated parcel dataset; the well was then assigned to the parcel and the ET_Status was

changed to “ManualAssign”. When no irrigated area was found, the ET_Status was changed to no

assignment (“NA”) and the well was not assigned to any parcel.

As described in the Subtask 1.3 Memorandum5, HRS digitized the irrigated parcel snapshots using the

2010 irrigated parcel dataset as a starting reference file, then created irrigated acreage coverages going

backwards in time. For each snapshot year, all existing parcels were examined and edited where

5 ArkDSS Task 1, Spatial System Integration Component Subtask 1.3, Historical Irrigated Acreage Snapshots (May 10, 2019)

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changes had occurred; additional irrigated areas that were observed as part of this process were

digitized and added to the dataset. However, irrigated areas that were not near any already digitized

parcel(s) would not have been observed and thus would not have been digitized. This explains why a

small number of parcels were added as part of the well to parcel assignment process.

Figure 4. Original well location and snapped well location

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Figure 5. Flow chart displaying steps followed during the inspection phase

For all eight of the historic well datasets most of the wells were automatically snapped to irrigated

parcels and most of the remaining wells were manually assigned to an irrigated parcel (Figure 6). Wells

that were not snapped or manually assigned were in areas without reasonably nearby irrigated parcels

or irrigated areas. Most of these un-snapped wells were located outside the HI Model Boundary (see

Figure 7).

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Figure 6. “ET_Status” of historic wells per snapshot year – snapped, manual assign, and NA

Figure 7. Example of a well that was not snapped to a parcel

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Assign Well Attribute Data to Irrigated Parcels HRS applied the historic wells as irrigation sources to their associated irrigated parcels. This involved

adding the well’s WDID and ET_Status to the GIS attribute table of the irrigated parcel coverage. Two

main steps were followed to ensure that the attributes were applied appropriately:

Spatial Join – ArcMap’s ‘Spatial Join’ tool was used to join the well datasets’ key attribute fields

to the irrigated parcel dataset attribute table:

o WDID(s) – The unique well structure identifier from Hydrobase. When added to a parcel

in the irrigated parcel dataset, it identifies the well as a groundwater source for that

parcel.

o ET_Status – Indication of how the well was attached, or snapped, to the irrigated parcel.

Clean Up Attribute Table – The spatial join was performed as a ‘one to many’ relationship

between tables, which resulted in a row for each parcel and unique associated well. Thus,

parcels with more than one associated well contained an attribute row for each well (i.e. a

duplicate parcel). To remove the duplicate records, while retaining all relevant WDIDs, HRS

added the fields “WDID and WDID_01-WDID_056” to the attribute table (Table 5), where:

o WDID = Historic well WDID that was either snapped or manually assigned to the parcel

o WDID_01 – WDID_05 = Additional historic well WDIDs if more than one well was

snapped or manually assigned to a parcel.

Table 5. Excerpt of the attribute table for the irrigated parcel dataset, including joined attributes from the historic well datasets.

6 These fields were included in the datasets that HRS submitted to the SEO and Division 2 in May 2019. In the version of the data on the CDSS website, these field have been removed and the WDIDs have been added to the fields GW_ID1 to GW_ID20.

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Comments on Deliverable Limitations The process developed to assign historic wells to irrigated parcels introduced some limitations into the

final deliverables. These include:

The distance snapping approach did not account for physical barriers such as property lines,

roads, bodies of water, etc. For example, if a parcel across the street from a well was closer

than a parcel on the same side of the street, the well will have been snapped to the parcel

across the street.

A well may have been snapped to the neighbor’s irrigated parcel if that parcel was closer than

the well owner’s irrigated parcel.

A well may have been snapped to a certain parcel in one snapshot year, then snapped to a

different parcel in another snapshot year. This could occur due to the changing extent of the

irrigated parcels over the snapshot years, causing one parcel to be closer to the well in one

snapshot year, then further from the well in another snapshot year.

In summary, the method used to assign historic wells to the snapshot year irrigated parcels was

primarily based on the proximity of the well to a parcel and the completion date and abandonment date

of the well. In cases where there was no proximal irrigated parcel, HRS visually inspected the area

around the well and either digitized new irrigated acreage or associated the well with a slightly more

distant parcel that could reasonably be served by the well. While this method can be inexact at the

parcel level, we believe it provides a reasonable generalized representation of the location and history

of historic groundwater in Division 2.

Final Deliverables As per the Subtask 1.1.c scope of work and revisions thereto, HRS submitted the following data

deliverables:

Two file geodatabases containing wells inside the HI model area (HistoricWells_InsideHI.gdb)

and outside the HI model area (HistoricWells_OutsideHI.gdb)

o Each file geodatabase contained a point file for each snapshot year – 1954, 1975, 1988,

and 1998 (8 total point files):

HistoricWells_InsideHI.gdb

Wells_InsideHI_1954

Wells_InsideHI_1975

Wells_InsideHI_1988

Wells_InsideHI_1998

HistoricWells_OutsideHI.gdb

Wells_OutsideHI_1954




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As part of ArkDSS Task 1.3 HRS submitted the following deliverable, which included work done as part of

Subtask 1.1.c:

One file geodatabase containing the irrigated acreage for the snapshot years

(HistoricIrrigatedAcreage.gdb) with the newly applied groundwater sources

State Refinements Following HRS’s submission of deliverables, the state refined the assignments of the historical wells to

parcels within the final irrigated parcel datasets by examining available documents for each well

including permits, decrees, and DWR field inspection forms. Although many permits and decrees are

silent on place of use, many do indicate the permitted/decreed place of use while inspection forms

often provided some indication of the parcels on which wells were being used at the time of inspection.

Using HRS’s spatially based assignments as a starting point, a number of well assignments were altered

or added to additional parcels.

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