Water technical companion

How to read the water account

The question: How much water went through Homestake Tunnel, and how much passed Gold Park in the creek? We compare the same 18 water years at these two recorded routes. This tells us their relative scale. The Gold Park gauge is near the campground below the existing collection system; tributaries farther downstream belong to another comparison.

The records: Colorado's approved monthly tunnel exports and the USGS daily Gold Park flow are summed into acre-feet for each water year. The five collector records describe where and when water was first taken; much of that water later enters the tunnel account, so the collector and export totals are never added together. The main data sources are [WATER:TECH-01, -02, -05].

The separate basin check: For matching 2007-2020 years, mapped rain and snow precipitation is compared with the two recorded routes and the signed change in Homestake Reservoir storage. Snow loss to the air, reservoir evaporation and fen water use are estimated separately. What is left stays visibly unassigned; it is not labeled groundwater loss. Equations, annual rows, source versions, and replication files follow below. [WATER:TECH-03, -05]; PRISM Climate Group precipitation methods.

Water years 2007-2024 cover October 1, 2006 through September 30, 2024.

Technical companion

Detailed accounting, basin comparisons and source records. Read the Water Findings brief for the main summary.

At Gold Park, the annual-average tunnel export to Turquoise Lake exceeded the creek flow passing the gauge in WY2007-2024. The matched means are 23,370.94 and 21,498.22 AF/year, respectively. The separate WY2007-2020 precipitation closure tests signed storage and estimated natural processes. The two-route percentage remains a scale comparison, not a verified percentage of native runoff for the full valley or each colored basin.

23,370.94 AF/year

Through Homestake Tunnel to Turquoise Lake, WY2007-2024.
420,676.9294 AF / 18 years. [WATER:TECH-01, -21]

13,148.95 AF/year

Five recorded collector intakes, WY2014-2024. These volumes overlap later tunnel exports and must not be added to them. [WATER:TECH-02]

About 52% at Gold Park

WY2007-2024. The gauge’s published drainage area is 35.6 square miles; the point-specific StreamStats polygon used for the precipitation calculation is 35.9029 square miles, about 0.85% larger. Export comparison is 52.09% before corrections, 51.75% with storage and recorded evaporation accounts. Partial balance. [WATER:TECH-01, -03, -05]

About 43% at Red Cliff

WY2007-2011; 58.2 mi2 drainage. Corresponding comparisons are 43.04% and 43.08%. A different basin and period, not an uncertainty range for the full valley. [WATER:TECH-01, -03, -18]

Map retains upvalley at the top. Colored areas end at stream junctions; intake catchments end at the intakes. Red Cliff town and gauge 09064500 are separate. French Creek joins above Gold Park. The new Missouri gauge is below Sopris and above Fancy. [WATER:TECH-05, -06]

E. Upper Homestake: the native-coded storage plus direct-flow ledger averages 13,306.09 AF/year in WY2014-2024. That is a source-coded accounting subtotal, not a verified E-basin capture total. Its unresolved physical reconciliation is on the Upper Homestake section.

How much do the remaining gaps matter?

Cumulative downstream balances: useful average comparisons, with the unmeasured corrections left visible.

At a gauge below all existing collection points, reservoir releases and collector transfers are internal movements already reflected in downstream flow. Do not add them again. Tunnel export is recorded separately from these internal movements. Long-term storage changes telescope to ending minus beginning contents.

N = Q + E + change in storage + L - X + C
N: no-project runoff at the gauge; Q: observed creek; E: basin export. L: incremental project losses relative to the former landscape; X: external physical replacement inflow; C: other net depletions and measurement/routing corrections. L, X and C are not yet fully bounded.

Matched WY2007-2020 precipitation closure

In plain terms, this calculation starts with the PRISM estimate of rain and snow falling inside the mapped Gold Park drainage and subtracts the measured tunnel and creek routes, then accounts for the reservoir gaining or losing stored water. The result is the amount left for natural losses, other storage, boundary flow and measurement or model error. Estimates for snow loss to the air, reservoir evaporation and fen water use could explain part of it without assigning the balance to any one cause.

Calculation and source treatment

The basin equation is R = P − E − Q − ΔS, where R is the storage-adjusted remainder, P is modeled precipitation, E is approved tunnel export, Q is integrated Gold Park discharge, and ΔS is end minus beginning reservoir storage. All terms are in acre-feet over the same water years. Positive ΔS stores water and negative ΔS releases it. The precipitation source is PRISM Climate Group; the drainage boundary is the USGS Gold Park StreamStats basin. DWR export and reservoir records and USGS gauge records are [WATER:TECH-01, -03, -05].

The current 800-m PRISM clip to the 35.9029-square-mile Gold Park StreamStats basin gives 860,946.71 AF of rain plus snow water-equivalent precipitation, or 61,496.19 AF/year. Approved tunnel export totals 326,827.91 AF and integrated Gold Park flow totals 326,778.27 AF. P-E-Q is 207,340.54 AF, or 14,810.04 AF/year. Homestake Reservoir storage declined 642.30 AF from the September 2006 endpoint to the September 2020 endpoint. With positive delta storage defined as water retained, P-E-Q-delta S is 207,982.84 AF, or 14,855.92 AF/year.

Historical September 24 scenario: 247-353 mm of fen evapotranspiration in normal years. The current table below includes the drought year, using 101-353 mm.

The snow range uses regional studies and is not a calibrated Gold Park measurement. Sexstone's 2018 regional model includes surface, canopy and blowing-snow sublimation and averaged 28%; applying that regional percentage nearly consumes the full closure, so it is retained as a sensitivity warning. The often-cited 40% figure comes from dense mature boreal spruce and is not applied basinwide. The reservoir scenarios use fixed 278.4- and 333-acre surfaces. DWR's 237.58-AF/year evaporation account is administrative and is not added to gross physical evaporation.

Year-by-year water balance

Positive reservoir delta S retains water; negative delta S is drawdown and supplies water. WY2009 and WY2012 demonstrate why the sign matters. WY2014-WY2016 remain NA individually because only the combined +41,384.87-AF repair-period change from September 30, 2013 to September 29, 2016 is supported.

Plant, soil, wetland and groundwater terms

The exact basin clip contains 11.593 confirmed fen acres and 153.731 potential fen acres. The overlapping NWI inventory contains 332.104 acres of vegetated or other wetlands. Blanken 2014 Table 5 reports a full 101-353 mm partial-season ecosystem flux at High Creek, including the drought year. Applied to the mapped 165.324 acres, this produces the 55-191 AF/year fen estimate and includes vegetation, soil and wet-surface vapor flux on those acres.

Annual fen and wetland storage change remains an unknown signed term. Each 0.1 foot of mean water-equivalent endpoint change equals 16.53 AF over mapped fens or 33.21 AF over the broader vegetated-wetland footprint. These are sensitivities, not observed losses. Recharge and later baseflow are internal and Gold Park Q already includes return flow. No public DWR or USGS monitoring point inside the exact basin supports an annual aquifer-storage or net boundary-flow volume.

If the full open remainder were land ET, a 60/40 closure allocation would give 2,575-4,153 AF/year of transpiration and 1,717-2,768 AF/year of soil plus wet-canopy evaporation. Those figures are conditional ceilings, not estimates, and would leave nothing for storage, groundwater flow or error. Published local warm-season ET depths overclose the remainder when transferred basinwide, which is evidence of scale, phase, land-cover, boundary and input mismatch.

September 24 historical workbook · September 24 historical scenario ledger · component and source-status table

Carryover is substantial in individual years: the +1,011.50 AF endpoint change, or +56.19 AF/year over 18 years, is the net of large drawdowns and refills. Approved September 30 contents fell 20,630.14 AF in WY2009, recovered 15,909.39 AF in WY2010, and fell 39,421.17 AF in WY2012 while Reclamation reports dam-face and outlet repairs. Storage near the end of WY2012 was 275.52 AF. The repair work continued through WY2014; the reservoir completed refilling in WY2015. Annual precipitation and outflow comparisons must use signed storage changes where both endpoints exist. DWR September 30 endpoints for 2014-2016 and 2021 are absent from this snapshot. [WATER:TECH-03, -19]

A release can draw on earlier years' water: DWR's September 2020 pilot released 1,666.9 AF down Homestake Creek past Gold Park during a downstream call, while WY2020 net storage fell only 763.78 AF. The one-time pilot tested potential state-line delivery. Gross creek releases already enter Gold Park gauge flow and are not a third export route. [WATER:TECH-03, -20]

Repair-period sensitivity: pooled tunnel share is 52.09% across all WY2007-2024, 51.23% excluding repair WY2012-2014, and 52.94% also excluding refill WY2015. All years stay in the main comparison. Annual accounting still needs signed storage and operating context. [WATER:TECH-01, -03, -05, -19]

Conditional net creek-flow reduction uses a different numerator, with all terms pooled: (E + storage change + recorded evaporation) / (Q + E + storage change + recorded evaporation) = 52.40% Gold Park and 43.00% Red Cliff. These are not bounds on export share. Full-mouth and individual intake-catchment percentages remain unresolved.

Coverage: Gold Park 6,575 Approved daily values, 2,876 estimated; Red Cliff 1,826, 1,311 estimated. Red Cliff Q uses preserved DWR-published USGS annual totals; current USGS daily integration is 19.8672 AF higher over five years, changing the comparison by only 0.0026 percentage point. Sources and versions are retained separately.

E. Upper Homestake: the real balance

Worked water year: 1 October 2023 through 30 September 2024. Source precision is retained for reproducibility.

All five collection systems convey water into Homestake Reservoir. The tunnel draws from the reservoir. A “direct” tunnel account is an accounting category for pass-through water, not evidence of a separate pipe. The two outlet records must stay separate: the 2020 report does not instruct summation, and 2026 field notes place GH2 upstream of GH1. [WATER:TECH-04, -12]

A useful diagnostic, still short of native runoff

N* = verified outlet Q + export + change in storage + recorded evaporation - collector imports
= Q + 18,151.9788 + 7,550.1550 + 278.3126 - 12,163.9310
= Q + 13,816.5154 AF before unresolved physical corrections.

A native stream-inflow estimate would also depend on precipitation directly on the reservoir, any physical external replacement inflow, net seepage losses, other inflows, measurement corrections and the short downstream increment to mapped basin E. The evaporation account may already be net of some terms; its exact basis remains unresolved.

Using outlet channel 1 alone gives 16,793.5071 AF. The unresolved relationship between the two outlet records and other physical corrections prevents a verified E-basin runoff total. Changing the feeder-account basis shifts the result by 1,367.0698 AF. A calibrated confidence interval and runoff percentage remain unresolved.

Unresolved parts of the E-basin account: source ledger and corrections; inlet/bypass/spill/seepage topology and historical ratings/shifts; evaporation/precipitation basis; surface area and reservoir-native boundary. The cumulative-balance section separately compares recorded tunnel exports with flow at the downstream Gold Park gauge.

Native runoff: every basin has a status

“Unknown” identifies a quantity that the available matched records have not yet resolved.

* WY2007-2024. Red Cliff uses WY2007-2011; collector/coded means use WY2014-2024. Parent areas overlap: do not sum rows. **E is a ledger subtotal, not verified capture. Missouri gauge excludes Fancy. Gray drainage is not one uniform lower-valley basin. Basin A extends below Red Cliff to the Eagle River.

What the official natural-flow model adds

The official 2024 StateMod release still ends its natural-flow inputs in WY2013. It groups Homestake into reservoir + East Fork and a combined French/Fancy/Missouri/Sopris system. It has no separately validated native series for every map polygon. Its Gold Park natural-flow input totals 264,026 AF in WY2007-2011 and 325,557 AF in WY2007-2013. These historical model values and full monthly inputs are supplied separately. [WATER:TECH-07]

For the same WY2007-2011 window, our Gold Park partial balance totals 262,918.84 AF, 0.42% below the model. This is a consistency check with shared inputs, not independent validation or proof of individual-basin shares.

Two paths at the measured gauges

Ratios use matched recorded diversion/export and observed creek flow. They are not precipitation, snow or natural-flow fractions. Gold Park (35.6 mi2) cannot replace the Red Cliff basin (58.2 mi2). [WATER:TECH-01, -02, -05, -06]

Missouri/Sopris measurements

USGS 09063900: 6.38-square-mile gauge drainage. Below Sopris; above Fancy. Intake accounting paired only to those sources.

Volume-weighted WY2014-2024: 46,510.7155 AF captured / (46,510.7155 + 59,227.6165 AF observed creek) = 43.9866%. Observed creek branch = 56.0134%. This is a two-route comparison. All 4,018 dates have Approved values; many are estimated daily discharges, retained as such. [WATER:TECH-02, -05]

WY2024 example: (1,402.6896 Missouri + 2,308.3006 Sopris) / (3,710.9902 + 6,514.5917 creek) x 100 = 36.2912%. Across years use the ratio of summed volumes, not the average of annual percentages.

Dry versus wetter season: May-July 2018 had 8.795 cfs mean observed creek flow and a 73.12% two-path capture share. May-July 2019 had 35.176 cfs and a 43.15% share. In August-September 2018, capture was recorded as zero while the creek averaged 1.096 cfs, with a 0.403 cfs minimum 7-day mean.

Sensitivity: omit unresolved zero-capture WY2016 and the pooled share becomes 48.1161%. An illustrative +/-10% change to creek Q gives 41.6535-46.5967%; this is not a statistical confidence interval. Five-collector capture is concentrated in spring: 88.2613% in May-June, 99.2952% in May-July. [WATER:TECH-02, -05]

Missing cfs: rights and creek flow differ

Legal diversion rates, bypass obligations and measured discharge each answer a different question.

Current DWR net-amount records and 2025 city exhibits agree. French 60.10 + 2.08 = 62.18 cfs; East Fork 70.80 + 3.83 = 74.63 cfs. Older tables carry stale amounts. Bypass list also includes Middle Fork 6, Gold Park 24 and Fall 3 cfs. These are specified amounts, not evidence of actual continuous discharge. The retained record does not resolve the full seasonal and low-natural-flow rules in the governing decrees and permits. [WATER:TECH-08]

Whitney-related conditional rates

These rates describe a rights inventory, not selected collection works or annual yield. Do not add Fall 260 + 250 or Peterson 50 + 70. Eagle-Cross has a 300 cfs new-right aggregate and a described 400 cfs system conveyance ceiling inclusive of changed older rights. Resolution Reservoir’s 5,000 AF right is storage, not cfs. [WATER:TECH-08]

Fall, Peterson and Resolution: the source landscapes

The utilities' March 2022 concept describes gravity collection from Peterson, Fall and Resolution creeks to a new Homestake Creek reservoir, then pumping into existing Homestake Reservoir. The July 2019 concept map instead depicts an Eagle River collection point below Resolution. These are dated alternatives; the final intake locations, alignments, access and power route remain unresolved in the reviewed record. CSU March 2022 fact sheet, pp.1-2 · July 2019 concept map.

All three creeks flow to the Eagle. Resolution joins above Homestake's confluence; Peterson and Fall join below it. Water removed from a donor creek affects the route downstream of its intake, while construction and groundwater disturbance can reach beyond the channel.

Whole-basin mapped resources, October 8, 2026 analysis

The National Wetlands Inventory polygons were clipped to USGS NLDI whole catchments and unioned within each class. Source imagery includes 1983 and 2011; about 7 percent of Resolution's basin has 2011 coverage. These are mapped resource inventories, with ponds listed separately. They are neither a fen-only inventory nor the predicted acreage damaged by a selected intake. They are also separate from the Whitney-to-Eagle 362.1-acre connected-complex assessment and the modeled Whitney full-pool footprints. Inventory methods and source identifiers · USFWS inventory · USGS catchments.

Fall Creek has a documented conservation history. CNHP's 2000 Eagle County survey described its willow carr and sedge wet meadows as high-quality habitat in excellent condition and warned that diversion would significantly disrupt them. The conservation area's 1,139 acres describe the supporting landscape, not wetland acreage. CNHP survey, pp.149-150.

The physical consequences extend through the collection system: reduced or retimed flow, altered shallow groundwater, habitat fragmentation, trenching and excavation, access roads, tunnels, pumping and power. These source landscapes retain ecological and wild-place value beyond formal Wilderness boundaries. Their condition belongs alongside the reservoir footprint in evaluating permanent loss.

The same 2022 fact sheet describes a broader additional average annual city-supply objective of 20,000 acre-feet and storage alternatives of 6,850 to 20,000 acre-feet. Annual supply and reservoir capacity are different quantities. The objective is not a fixed annual allocation to these three creeks. Read the agreements guide's water quantities.

Accounting evidence and unresolved terms

The March 2022 official factsheet remains the current linked version: Whitney storage alternatives are 6,850-20,000 AF; up to 20,000 AF/year is the broader Eagle River Joint Use objective. A current Whitney-only dependable-yield result remains unavailable in the reviewed record. A February 24, 2026 signed City resolution and related Otero/Wild Horse agreements document a conveyance connection. [WATER:TECH-09, -10]

The reviewed public record does not establish dated selected-design GIS, a governing rights-to-intake matrix or a daily with/without-project model. Older official court records identify specific engineering and yield studies. These historical studies document earlier engineering work; a current Whitney yield result is not available in the reviewed record.

Whitney-only additional export remains unknown. Hypothetical 0 / 2,500 / 5,000 / 10,000 / 20,000 AF/year increments are sensitivity inputs, not yield predictions. Available capture at each intake and day depends on flow after applicable bypasses and prior rights, together with pumping, conveyance and storage limits.

Additional public measurements

Additional measurements and technical records through September 23, 2026.

Findings that shape the interpretation

Do not add outlet records: DWR’s 2020 release analysis uses 174 cfs while DISCHRG2 separately records about 20 cfs. A 2026 field note identifies GH2 upstream of GH1. Channel-specific measurements narrow the issue, but the historical configuration and rating sequence remain a material limit. [WATER:TECH-04, -12]

Historical peak and low-flow measures changed differently: the 2005 Eagle River Inventory reports Gold Park’s average annual 1-day maximum declining from 640 to 230 cfs between its 1947-1953 and 1972-2001 periods, while its 7-day minimum increases from 3.4 to 4.8 cfs. These are historical observed-period comparisons with different climate windows, not modern causal estimates. The different peak and low-flow trends show why season and operating rules matter. [WATER:TECH-16, printed pp. 91-92]

Named model records exist: official documents identify the January 2012 and January 2013 Water Yield Estimates for Homestake Project Expansion Options, CSU’s TM #11 - IWRP Modeling Systems, and Aurora’s referenced Gibbens Data 040704.xls. These studies document earlier engineering work. A current Whitney-only dependable-yield result remains unavailable in the reviewed record.

Wild Horse South: Aurora announced a shift to Wild Horse South on 13 February 2026. Its February Q&A says existing rights and Otero would supply it without additional diversions. The reviewed public record does not include daily source-specific operations, so it does not quantify a change in Homestake exports. The 2023 BLM investigation maps concern the earlier site. [WATER:TECH-17]

Accounting differences and their effects

Hydrologic effect, legal compliance and ecological damage attribution remain separate determinations.

What the records establish and leave open

The matched tunnel and gauge records establish the scale of recorded exports and downstream flow. A complete post-2011 Red Cliff or full-mouth balance remains unresolved, as do incremental reservoir losses, other net depletions and physical external replacement inflows. Those terms determine how far the partial balance could shift.

WY2024 provides the worked upper-reservoir account. Stage records measure water level; conversion to discharge depends on the applicable validated rating.

The retained Wild Horse agreements establish a system connection. Source-specific release and refill operations, and their effect on Homestake exports, remain unresolved.

Streamflow, groundwater supply, temperature and habitat describe different parts of the valley’s water system. A release below an intake leaves the upstream reach unrestored; the flow account does not quantify the response of each fen or streamside habitat.

Sources, definitions and replication

Primary records retrieved 23 September 2026 unless the original snapshot states otherwise. Exact UTC timestamps and SHA256 hashes travel with the data.

[WATER:TECH-01] DWR exports Approved monthly class 13704614, WDID 3704614. Original SQLite and source packet. Open DWR export records.

[WATER:TECH-02] DWR collector accounts WDIDs 3701253 / 3701254 / 3701255 / 3701256 / 3704644; total classes only. Open DWR collector records.

[WATER:TECH-03] DWR reservoir and telemetry WDID 3704516 stagevolume and monthly records; HOMOUTCO DISCHRG and DISCHRG2. Open DWR reservoir records.

[WATER:TECH-04] DWR pilot release report 1 April 2021. PDF p. 20 calibration; Appendix A pp. 46-47 physical routing/two flumes. Open DWR pilot release report.

[WATER:TECH-05] USGS daily discharge 09063900 Missouri, 09064000 Gold Park, 09064500 Red Cliff. Qualifiers preserved. Open USGS daily discharge records.

[WATER:TECH-06] USGS Gold Park station description 2003 annual record: gauge downstream from French. Current gauge area is 35.6 mi2; historic page says 36.0. NLDI/NHD polygons are modeled junction catchments. Open USGS Gold Park station description.

[WATER:TECH-07] Official StateMod inputs Upper Colorado cm2015 and Shoshone 2024 update. Natural-flow record ends 2013. Open StateMod model inputs.

[WATER:TECH-08] Rights and bypass sources Live DWR netamount; June 2024 Division 5 resume, pp. 21-26; September 2023 resume, pp. 23-24; 2025 city exhibits. All direct URLs in rights source index. Open water-rights application resume.

[WATER:TECH-09] CSU ERJU factsheet March 2022, 2 pages. Open CSU project fact sheet.

[WATER:TECH-10] City File 26-058 Adopted 24 February 2026; signed Resolution 11-26 and related Otero/Wild Horse IGA documents. Open City File 26-058.

[WATER:TECH-11] Cities’ final pilot verification 2 December 2021, PDF pp. 4-5 actual operations and non-refill finding. Open cities’ pilot verification.

[WATER:TECH-12] DWR outlet field measurements HOMOUTCO, 19 entries through September 2026; raw values, remarks and qualifiers preserved. Open DWR outlet measurements.

[WATER:TECH-13] USBR storage and operations Site 100120 daily storage and WY2024 operations report. Provisional series and endpoint comparisons in raw companion. Open USBR storage data.

[WATER:TECH-14] River Watch and EPA Water Quality Portal CORIVWCH_WQX-744; EPA NRSA UIDs 2012967/2013227/2014612. Query URLs and downloaded rows in source manifest. Open Water Quality Portal.

[WATER:TECH-15] USBR PAP-1088 July 2014, printed pp. 1, 3-4; PDF pp. 7, 9-10. Tunnel flume calibration, distinct from dam-outlet records. Open USBR tunnel calibration report.

[WATER:TECH-16] Eagle River Inventory 2005 CSU-authored assessment, author-hosted copy; printed pp. 84-94 historical hydrology. Open Eagle River Inventory.

[WATER:TECH-17] Aurora Wild Horse update 13 February 2026 South-site announcement and February 2026 presentation Q&A. Open Aurora Wild Horse update.

[WATER:TECH-18] Red Cliff preserved annual flow DWR-published USGS totals, retrieved 20 September 2026; original source redcliff-year and hash in database. Open Red Cliff annual flow records.

[WATER:TECH-19] Bureau of Reclamation Homestake repairs and refill, WY2012-2015 WY2012 section IV.D documents dam-face and outlet works repairs; WY2013 fa13.pdf section IV.D documents tunnel closure and continuing repairs; WY2014 fa14.pdf section IV.D documents renewed storage; WY2015 fa15.pdf Turquoise Lake section documents completed refill. Open Reclamation’s WY2012 report.

[WATER:TECH-20] Colorado DWR State Line Delivery Pilot Reservoir Release Report DWR 2021 report pp. 4-5 and 8-11: one-time September 23-29, 2020 release of 1,666.9 AF, purpose, Grand Valley call and Gold Park passage. Open DWR’s pilot release report.

[WATER:TECH-21] Aurora Water, Homestake Reservoir system description The reservoir page identifies the collection system and states that Homestake water goes through Homestake Tunnel to Turquoise Lake when needed. Checked 24 September 2026. Open Aurora’s reservoir description.

Arithmetic and reproducible files

Water year: October-September. DWR irrigation year: November-October. Capture is intake collection; export crosses the watershed divide; delivery is a later recipient/account quantity; consumption is depletion, not ownership. Water remaining in the creek is measured at a specified reach and time. Natural flow is the no-project counterfactual at that same location and time.

SELECT water_year, ROUND(SUM(volume_af),4) AS export_af
FROM diversion_month
WHERE water_class_num=13704614 AND water_year BETWEEN 2007 AND 2024
GROUP BY water_year
HAVING COUNT(DISTINCT month)=12
AND MIN(approval_status)='Approved' AND MAX(approval_status)='Approved';

AF = sum(daily mean cfs) x 86,400 / 43,560. The public evidence ZIP preserves calculation code, daily CSVs, source timestamps, hashes and caveats. The 41-sheet workbook retains live key formulas.