# Rainfall collection calculator

- Human page: https://happytails.ai/en/calculators/rainfall-collection-calculator/
- Markdown: https://happytails.ai/en/calculators/rainfall-collection-calculator.md
- Structured JSON: https://happytails.ai/agents/en/calculators/rainfall-collection-calculator/index.json
- Visibility: public

## Tool capabilities

| Property | Value |
| --- | --- |
| Tool ID | `rainfall-collection-calculator` |
| Category | calculators |
| Implementation | Registered implementation. Registration alone is not a production-quality guarantee. |
| Browser execution | Automatic updates after valid input or file selection. |
| Browser processing | Browser; see tool notes for network behavior. |
| HTTP API | Not callable through HTTP. |
| Browser-agent interface | run_current_tool |

### Implementation notes

Calculate one event’s potential runoff, first-flush loss, new storage and overflow. Assumes no water use during the event and makes no potability claim. Runs on your device. Changing units keeps the entered numbers.

### Inputs and settings

No free-text input is required. Use the file inputs and/or settings below.

| Setting | Meaning | Control type | Default | Constraints |
| --- | --- | --- | --- | --- |
| `area` | Horizontal projected catchment area | number | 100 | min=0 max=1000000000 step=any |
| `areaUnit` | Area unit | select | "m²" | Allowed: m², ft², yd², acre, hectare |
| `rainfall` | Rain depth in this event | number | 20 | min=0 max=1000000000 step=any |
| `depthUnit` | Water depth unit | select | "mm" | Allowed: mm, cm, m, in, ft |
| `efficiency` | Collection efficiency before first flush (%) | number | 80 | min=0 max=100 step=any |
| `firstFlush` | First-flush volume discarded | number | 50 | min=0 max=1000000000 step=any |
| `tankCapacity` | Tank capacity | number | 1500 | min=0 max=1000000000 step=any |
| `tankExisting` | Water already in tank | number | 200 | min=0 max=1000000000 step=any |
| `volumeUnit` | Volume unit | select | "L" | Allowed: L, m³, US gal, Imp gal, ft³, yd³ |

### Browser-agent workflow

1. Open the human page in a browser that supports WebMCP.
2. Discover the interface exposed by that page; use its actual schema.
3. Select files on the page first when the tool requires files.
4. Call `run_current_tool` with valid input and settings.
5. Inspect the returned result or error and the displayed output. Retrieve files from the displayed download links.

Calls do not automatically copy or download results. Browser permissions still apply. Interface availability alone is not proof of successful execution.

### Planning specification

One event with no water use during rainfall. Efficiency and first flush are supplied assumptions. No forecast, plumbing design or drinking-water suitability is implied.

This describes intended requirements. Use the implementation notes, interface schema and observed output to determine current support.

### Complete machine-readable capability record

```json
{
  "id": "rainfall-collection-calculator",
  "category": "calculators",
  "built": true,
  "requirements": "One event with no water use during rainfall. Efficiency and first flush are supplied assumptions. No forecast, plumbing design or drinking-water suitability is implied.",
  "implementation": {
    "fields": [
      {
        "key": "area",
        "label": "Horizontal projected catchment area",
        "value": 100,
        "type": "number",
        "min": 0,
        "max": 1000000000,
        "step": "any"
      },
      {
        "key": "areaUnit",
        "label": "Area unit",
        "value": "m²",
        "type": "select",
        "values": [
          "m²",
          "ft²",
          "yd²",
          "acre",
          "hectare"
        ]
      },
      {
        "key": "rainfall",
        "label": "Rain depth in this event",
        "value": 20,
        "type": "number",
        "min": 0,
        "max": 1000000000,
        "step": "any"
      },
      {
        "key": "depthUnit",
        "label": "Water depth unit",
        "value": "mm",
        "type": "select",
        "values": [
          "mm",
          "cm",
          "m",
          "in",
          "ft"
        ]
      },
      {
        "key": "efficiency",
        "label": "Collection efficiency before first flush (%)",
        "value": 80,
        "type": "number",
        "min": 0,
        "max": 100,
        "step": "any"
      },
      {
        "key": "firstFlush",
        "label": "First-flush volume discarded",
        "value": 50,
        "type": "number",
        "min": 0,
        "max": 1000000000,
        "step": "any"
      },
      {
        "key": "tankCapacity",
        "label": "Tank capacity",
        "value": 1500,
        "type": "number",
        "min": 0,
        "max": 1000000000,
        "step": "any"
      },
      {
        "key": "tankExisting",
        "label": "Water already in tank",
        "value": 200,
        "type": "number",
        "min": 0,
        "max": 1000000000,
        "step": "any"
      },
      {
        "key": "volumeUnit",
        "label": "Volume unit",
        "value": "L",
        "type": "select",
        "values": [
          "L",
          "m³",
          "US gal",
          "Imp gal",
          "ft³",
          "yd³"
        ]
      }
    ],
    "input": false,
    "background": false,
    "live": true,
    "presentation": "metrics",
    "note": "Calculate one event’s potential runoff, first-flush loss, new storage and overflow. Assumes no water use during the event and makes no potability claim. Runs on your device. Changing units keeps the entered numbers.",
    "experience": {
      "automatic": true,
      "single": false,
      "inputMaxLength": 1000000,
      "inputMode": "text",
      "label": "Your text",
      "placeholder": "Type or paste your input…",
      "help": "Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.",
      "action": null
    },
    "mode": "automatic",
    "interactive": false
  },
  "execution": "Browser interface",
  "api": null,
  "browser_agent": {
    "supported": true,
    "name": "run_current_tool",
    "discovery": "WebMCP on the human page in a supporting browser",
    "verification": "See audit/API-AUDIT.md; availability is not verification"
  }
}
```

## Page guide

Estimate recoverable rainwater, tank storage and overflow for one rainfall event.

How can we improve this tool?

Report a problem or share an idea.

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### How to use Rainfall collection calculator

1. Enter your measured quantities, units and assumptions.
2. Review the calculated result and the stated limits.
3. Download the report or plan for your project.

## Useful next steps

- [Garden irrigation calculator](https://happytails.ai/en/calculators/garden-irrigation-calculator/) ([Markdown](https://happytails.ai/en/calculators/garden-irrigation-calculator.md))

- [Pond volume calculator](https://happytails.ai/en/calculators/pond-volume-calculator/) ([Markdown](https://happytails.ai/en/calculators/pond-volume-calculator.md))

## Measure projected catchment area

Use the horizontal projected area and rainfall depth for the same event. Enter your collection efficiency and the first-flush volume you plan to discard.

### Check the tank balance

Subtract the water already in the tank from its capacity. The result separates rain on the catchment, recoverable water, newly stored water and overflow.

### Save the measurements and assumptions

Download CSV and a text or JSON report. The calculation runs on your device. Changing a unit keeps the number you entered, so check both before using the result.