Week 1 – Conceptual Models & Arid Hydrology (Arizona Case Study)

Upper Verde River (HUC8 15060202) — building defensible assumptions from public data

Week goals

By the end of Week 1, you will be able to:

  • Delineate a real basin using USGS StreamStats and extract basin characteristics
  • Build a defensible conceptual groundwater model for an arid/SW basin using proxy evidence
  • Identify likely recharge zones, flow directions, and discharge zones (with justification)
  • Write a short assumptions + uncertainty memo in a consulting style

Case study basin

Upper Verde River (HUC8: 15060202) :contentReferenceoaicite:2

Why this basin works for learning: - Arizona-relevant hydroclimate and mixed mountain/basin settings - Strong groundwater–surface water interactions (springs/baseflow on parts of the Verde) - Plenty of public context, but still “real-world messy” in terms of uncertainty

Tools you will use this week

  • USGS StreamStats (Arizona application) for basin delineation + basin characteristics :contentReferenceoaicite:3
  • A basemap viewer (web) and/or GIS (optional) for hillshade/geology screenshots
  • Your notes (markdown or a dedicated week-01-notes.md)

You do not need to build a numerical model yet. The job skill this week is: turning incomplete evidence into explicit, defensible assumptions.

Deliverables (you will publish these to your repo)

Create a folder: curriculum/week-01-deliverables/

By the end of the week, commit:

  1. upper-verde_streamstats_report.pdf (or HTML print) + upper-verde_basin_boundary.* if you export it
  2. figure_01_basin_overview.png (annotated screenshot map with basin outline)
  3. figure_02_conceptual_model_planview.png (your conceptual diagram)
  4. figure_03_conceptual_model_xsection.png (your conceptual cross-section)
  5. upper-verde_conceptual-model-memo.md (1–2 pages)

Daily plan (2–3 hrs/day)

Day 1 — Delineate the basin + collect the “minimum defensible dataset”

1) Delineate a watershed in StreamStats

Go to the USGS StreamStats Arizona application :contentReferenceoaicite:4

Do the following:

  • Use the map interface to select a point on the Upper Verde River network.
    • Choose a point that makes sense as a “project point” (e.g., upstream of a confluence, near a town crossing, or another recognizable location).
  • Run Delineate to generate the basin boundary.
  • Export:
    • Basin boundary (shapefile/geojson if available), OR at minimum a screenshot with the boundary visible
    • Basin characteristics report (download or print-to-PDF)

Deliverable: Save into curriculum/week-01-deliverables/: - upper-verde_streamstats_report.pdf - figure_01_basin_overview.png (screenshot of delineated basin + point)

2) Extract the “minimum dataset” from StreamStats outputs

From the StreamStats report, capture (copy into notes): - Drainage area - Mean basin elevation / relief (if available) - Slope metrics - Any climate/precipitation indices StreamStats provides - Any flow statistics (peak/low flow estimates) if available in AZ StreamStats

StreamStats provides GIS-derived basin characteristics and flow statistics in many regions; document exactly what it gives you for your point. :contentReferenceoaicite:5

3) Make a 1-paragraph basin description

Write a short description (5–8 sentences) summarizing: - Basin location / setting - General hydroclimate (arid SW) - What StreamStats says about size, elevation, slope - Why this is a groundwater-relevant basin (hypothesis to test later)

Day 2 — Build a defensible recharge-zone map (no “guessing”)

You will map recharge likelihood zones using proxy evidence.

Inputs (choose at least two)

Use StreamStats + one or more of: - Hillshade / DEM view (web map or GIS) - Geologic map screenshot (state or USGS) - Soils / land cover view (optional)

How to classify recharge zones (rules you must apply)

Create 3–5 “recharge likelihood” classes and justify them:

A. Mountain blocks / high elevation zones - Hypothesis: higher precip, runoff generation → potential mountain-front recharge (MFR) - Note uncertainty: fractured bedrock can transmit recharge, but spatially variable

B. Alluvial fans / basin-fill margins - Hypothesis: coarse sediments + focused runoff infiltration → higher recharge potential

C. Ephemeral channel corridors - Hypothesis: focused infiltration during stormflow; losing reaches likely in coarse alluvium

D. Basin floor fine sediments / high ET zones - Hypothesis: generally low diffuse recharge; high evaporative demand

Deliverable

Create figure_02_conceptual_model_planview.png: - Start with your basin overview (Day 1) - Add labeled polygons/regions for recharge likelihood classes - Add 5–10 annotation callouts (“Why this is likely a recharge zone”)

Also create a short table in your notes:

Recharge zone Evidence used Why plausible Biggest uncertainty

Day 3 — Infer groundwater flow directions + discharge zones (with explicit logic)

1) Flow directions (what you must do)

Sketch a potentiometric surface hypothesis using:

  • Topographic gradients as first-order control (mountains → valley)
  • Stream corridor as potential discharge zone (baseflow/springs) or losing zone (episodic infiltration)
  • Pumping centers (if you can identify municipal/ag regions from public info; if not, note as “unknown”)

You are not claiming truth — you are constructing a defensible first-pass hypothesis.

2) Discharge zones (identify at least 2 types)

Common arid/SW discharge mechanisms: - Spring discharge / baseflow to the river - Pumping (anthropogenic discharge) - Riparian ET (phreatophytes) where shallow water table exists

Deliverable

Create figure_03_conceptual_model_xsection.png: - Cross-section from highlands → basin fill → river corridor - Include: - Hydrostratigraphy (bedrock vs basin fill) - Water table shape (conceptual) - Recharge arrows (by zone) - Discharge arrows (river/baseflow, ET, wells) - A note identifying “unknowns” (e.g., depth to bedrock, K contrasts)

Write 8–12 bullets answering: - “If challenged, what evidence supports my flow direction arrows?”

Day 4 — Data constraints + “defensibility audit”

Make a table (this is a consulting staple):

Unknown / data gap Why it matters How it could change conclusions What proxy you used

Examples of typical arid-basin constraints: - Sparse head observations (few wells) - Poorly constrained hydraulic conductivity zonation - Recharge magnitude & timing unknown - Stream–aquifer interaction unknown (losing vs gaining varies) - Pumping time series unknown

Then write two lists:

Most defensible assumptions (5–8)
Most vulnerable assumptions (5–8)

Finally, write 3 “challenge questions” someone could ask in a review: - “How do you know recharge is focused there?” - “Why is that boundary no-flow?” - “What evidence supports gaining vs losing reaches?”

Day 5 — Write the conceptual model memo (portfolio piece)

Create upper-verde_conceptual-model-memo.md_