2021-06-01_HYDROLOGY - M1994027

• Permit No: M1994027
• IBM Index Class Name: Hydrology
• Doc Date: 6/1/2021
• Doc Name: Substitute Water Supply Plan
• From: DWR
• To: DRMS
• Email Name: ECS
• Media Type: D
• Archive: No

Aggregate Industries South Platte Combined SWSP June 1, 2021
Plan IDs 3614, 4773, 3624, 4772, 4616, 3437, 3376, 3650, 3668, 5475, 5829, &t 6090 Page 12 of 23
The decree entered in case no. 2016CW3186 relied on a parcel-specific analysis of the
historical consumptive use of the subject water rights, with a study period of 1950 through 2001.
The total shares include 4/61" (0.667) of a share historically used to irrigate the Broncucci (aka
Wattenberg) Property. An average of 42 acres of pasture grass were irrigated by controlled flood
irrigation. The engineering study commissioned by Westminster for case no. 2016CW3186 found the
average historical consumptive use for the 0.667 Brighton ditch shares used on the Broncucci
Property to be 82.5 acre-feet.
The other 0.371 shares were historically used to irrigate the Haake Property, along with 5.75
shares of the New Brantner Extension Ditch Company. Irrigated portions of the Haake Farm ranged
from 92.3 to 111.8 acres from 1950-2001. During the study period, between 10.7 and 11.3 acres of
dry beans (prior to 1960) and corn (1960 on) were irrigated by the Brighton Ditch shares only; 20
acres of pasture grass and between 14.2 and 20.1 acres of dry beans (prior to 1960) and corn (1960
on) were irrigated by the New Brantner Ditch shares only; and between 49 and 61 acres of furrow
irrigated corn and flood irrigated pasture grass were irrigated by both the combined Brighton Ditch
and New Brantner Ditch water supplies. The engineering study commissioned by Westminster for
case no. 2016CW3186 found the average historical consumptive use attributable to the 0.371
Brighton Ditch shares used on the Haake Property to be 67.85 acre-feet.
The total average historical consumptive use for the subject 1.038 shares is therefore 150.35
acre-feet per year (144.85 acre-feet per share). Aggregate will utilize the entire 1.038 shares for use
in this plan. The use of the Brighton Ditch shares in this plan must comply with the terms and
conditions of the 2016CW3186 decree, including the volumetric limits identified in paragraph 35.1) of
the decree and summarized in the table below.
Apr May Jun Jul Aug Sep Oct Annual
Max Monthly and Annual Limits 59.7 96.3 96.3 106.6 97.8 56.8 52.3 458.0
20-Year Limits 458 1,073 1,355 1,598 1,375 879 425 7,163
For the purposes of this SWSP, you have estimated the expected credit for the Brighton Ditch
shares from a dry-year farm headgate delivery (using a 25% ditch loss, consistent with case no.
2016CW3186) of 331 acre-feet per share, or 343.60 acre-feet for all 1.038 shares for the period of
April through October. This amount is less than the 20-year average annual limit of 358.15 acre-feet
(7,163 acre-feet = 20 years), and therefore is acceptable.
The historical return flows associated with the 1.038 shares that are the subject of this SWSP
must be maintained in accordance with the return flow factors identified in paragraph 35.F of the
decree entered in case no. 2016CW3186. The return flow obligations will be accounted for and
replaced under this SWSP.
The total consumptive use credit for 2021 is projected to equal 203.79 acre-feet, which is
greater than the dry-year yield because of the reduced subsurface return flow obligation
requirement resulting from low deliveries in 2020. Aggregate anticipates utilizing the augmentation
structures on the Brighton Ditch operated by the City of Aurora for the delivery of these shares.
Replacement Summary
The proposed depletions and replacements are shown in the attached "South Platte Combined
Substitute Supply Plan Accounting 2021". The transit loss for each stream was estimated as 0.5% per
mile for the South Platte River and for the Cache la Poudre River east of Interstate 25, and 0.25% per