×

User-guide for Demand Base Calculator

The calculator can calculate the required quantity of water for drinking, cooking, bathing, sanitation, and gardening during long dry spells to fulfill diverse requirements per family. Past survey data of water usage per family in Sri Lanka were embedded therefore end-user can handle it easily, to calculate reliable and precious water requirements, and also, it can handle user-defined values of requirements.

Mathamatical equation used for calculations

Tank capacity (m³)=(Number of persons per familty × Water usage per person per day (L) × Number of dry days)/1000

User can enter any numeric values as input fields in (A), (B) and (C) sections.

Please note that calculations are applicable only for relevant measurement units of input fields{Water usage in "L" and the results is appeared in "m³"} in section (D).

If the user doesn't have an idea about the daily water requirement per person then the user can use the checklist under section (E). Under this section, the research values of past surveys are embedded for easy handling. (User can simply check and uncheck list option then values are automatically transferred into section (B) and removed from section (B).

Research Values

Drinking water requirement per person (L) : 4

Cooking water requirement per person (L) : 1

Sanitation water requirement per person (L) : 20

Washing water requirement per family (L) : 25

Gardening water requirement per family (L) : 30

×

User-guide for Yield Base Calculator

This calculator can calculate the monthly harvestable water volume stand on past rainfall values, user-defined roof catchment type, and area. Moreover, a separate option is provided to insert customized rainfall values without selecting district rainfalls

Mathamatical equation used for calculations

Tank capacity (m³) = (Roof Runoff Coefficient × Roof area (m²) × Monthly Rainfall (mm))/1000

Under section (A), the user can select the required roof type from different six options in the dropdown list then the relevant roof runoff coefficient value is selected (Roof runoff coefficient is the fraction of rainfall that appears as runoff on the roof).

In section (B)/(C), the user can enter the required fields for the dimensions of the roof in feet or meters (Refer to the figure below for selecting dimensions).

In section (D), users can select the lived-in district or required district then average rainfall values of over ten years data are selected.

In section (E), the user can select the desired month in the year (Please note that this calculator allows the user to calculate harvestable volume monthly).

In section (F), the user can enter the customized value. If the user is using this option, fields in (D) and (E) should be empty.

In section (G), the harvestable water volume is displayed in m³. Please note that select only dropdown values in sections (A), (D), and (E).

Research and Theoritical Values

Foof runoff coefficient (RC)

Average rainfall values

×

User-guide for Feasiability of Proposed Tank Capacity Calculator

This calculator can produce a graphical interpretation of the remaining water at the end of the month throughout the year based on proposed tank capacity and water consumption. Also, satisfaction percentage at the end of the particular month upon monthly demand is displayed for better understanding of end-user. This simulation was derived from some assumptions to keep the model simple. (Assumption: remaining water volume at the end of the month will be the water volume to next month consumption and harvestable yield in the same month is added to remaining water volume at the end of the same month)

Mathamatical equation used for calculations

V = v-D+Y

V = Starting Water volume in tank at the beggning of the month (m³)

v = Remaining water at the beggning of previous month (m³)

D = Monthly demand or Requirement (m³)

Y = Harvestable water in previous month (m³)

Users can enter any numeric values as input fields in section (A). As an in-demand base calculator monthly water requirement per person can be selected from the checklist under section (H).

In section (C), users can select the lived-in district or required district then average rainfall values of over ten years data are selected.

Under section (D), the user can select the required roof type from the different six options in the dropdown list then the relevant roof runoff coefficient value is selected (Refer user guide in yield base calculator).

In the section (E)/(F), user can enter the required fields for the dimensions of roof in feet or meters (Refer the figure in yield base calculator guide).

In section (G), the user can enter tank capacity manually or select value from the dropdown list, then remaining water dispersion throughout the year is plotted on a bar chart with the upper bound of entered tank capacity. Along with this, another bar chart of satisfaction percentage over demand is plotted. Numerical values of the remaining water and satisfaction percentage can be seen by hovering the mouse pointer on each bar (Refer to the figure below).

×

User guide for Bill of Quantity Estimation

This calculator enables to user to get idea about the construction cost of Rainwater Harvesting System.

This calculator is applicable only for the designs of roof rainwater harvesting systems including ferrocement or PVC tanks with PVC plumbings and spares. Please use only the options in dropdown lists for cost estimations where relevant up-to-date prices of tanks and other required spares are included for precious estimations.

If the user doesn't have an idea about the required fittings and spares for constructing the entire rainwater harvesting system then the user can get costs related to the most basic design based on your house dimensions.

If user needs costamized design then you can select the descriptive item check box then requried materials and spare list will popup. Here user can enter amount of required and calculated the cost for your costamized design.

Please note that appered estimated cost includes 15% additional cost from total cost of construction to cover any loss due to under estimations or price changes of materials and spares.