# Model Documentation

### | Version 4.0

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# 42_water_demand

# Water demand (42_water_demand)

## Description

The water demand module determines the water demand in the following sectors: agriculture, industry, electricity, domestic and ecosystem. Different scenarios for different water demand and environmental flow protection are possible. The module receives information from the 17_production, 30_crop, 09_drivers and 43_water_availability modules. It passes information to the module 43_water_availability and 11_costs.

## Interfaces

Interfaces to other modules

### Input

module inputs (A: agr_sector_aug13 | B: all_sectors_aug13)
| Description | Unit | A | B
--- | --- | --- | --- | ---
im_development_state (t, i) | Development state according to the World Bank definition where 0=low income country 1=high income country in high income level | \(1\) | x |
im_gdp_pc_mer (t, i) | Per capita income in market exchange rates | \(USD_{05MER}/cap/yr\) | x | x
im_wat_avail (t, wat_src, j) | Water availability | \(10^6 m^3/yr\) | x | x
vm_area (j, kcr, w) | Agricultural production area | \(10^6 ha\) | x | x
vm_prod (j, k) | Production in each cell | \(10^6 tDM/yr\) | x | x

### Output

module outputs
| Description | Unit
--- | --- | ---
vm_watdem (wat_dem, j) | Water demand from different sectors | \(10^6 m^3/yr\)

## Realizations

### (A) agr_sector_aug13

This realization models agricultural sector water demand endogenously, while other sectors are kept exogenous; Various settings for environmental water demand described below.

Agricultural water demand:

Water demand for agriculture is endogenously calculated based on irrigated cropland `vm_area(j,kcr,"irrigated")` and livestock production `vm_prod(j2,kli)`.

Irrigation water demand per area for each crop category and cluster is provided by the LPJmL model. This parameter refers to the water that has to be applied to the field, i.e. it includes losses due to evaporation on the field, but does not include losses during the water transport from source to field. Livestock water demand `ic42_wat_req_k(j,kli)` is derived from FAO data.

Irrigation efficiency:

Switches for different scenarios for irrigation efficiency can be chosen:

- A global static value of irrigation efficiency that is defined as the global weighted average of water losses from source to field ("conveyance efficiency times management factor") from Rohwer, Gerten, and Lucht (2007). Here, irrigated area from Siebert et al. (2007) has been used as aggregation weight.

- A regression of country values of the "conveyance efficiency times management factor" from Rohwer, Gerten, and Lucht (2007) on GDP.

Irrigation efficiency evolution with GDP for the SSP2 scenario.

Non agricultural human water demand:

Water demand from all other sectors is treated exogenously. The scalar `s42_reserved_fraction` determines how much water is reserved for non agricultural purposes. Technically, it is assigned to industrial use, while demand for other non-agricultural sectors is set to 0. The default value is 0.5.

Environmental water demand

Environmental water requirements can be specified separately using the switch `s42_env_flow_scenario`. The following settings are available:

- No additional environmental flows are considered.
- A certain fraction of available water `s42_env_flow_fraction` is reserved for environmental purposes and consequently not available for agricultural activities (in addition to `s42_reserved_fraction`).
- Environmental flow requirements (EFR) are calculated from LPJmL inputs according to an algorithm by Smakhtin et al. (2004) on cluster level. Due to the fact that MAgPIE only considers available blue water during the growing period of the plants (43_water_availability), EFR are also only calculated during this growing period. They are reserved in addition to `s42_protected_fraction`. In the case of the absence of an environmental flow protection (EFP) policy, a base protection can be specified: `s42_env_flow_base_fraction`. Its default value is 5 % of available water.

Whether a potential EFP policy takes effect is determined by the parameter `f42_env_flow_policy`.

\[\begin{multline*} vm\_watdem("agriculture",j2) \cdot v42\_irrig\_eff(j2) = \sum_{kcr}\left( vm\_area(j2,kcr,"irrigated") \cdot ic42\_wat\_req\_k(j2,kcr)\right) + \sum_{kli}\left(vm\_prod(j2,kli) \cdot ic42\_wat\_req\_k(j2,kli) \cdot v42\_irrig\_eff(j2)\right) \end{multline*}\]

`vm_watdem` is composed by irrigation and livestock demand uses. The factor `v42_irrig_eff` corresponds to the amount of water that is used inefficiently in the irrigation process.

> Limitations The module uses the "conveyance efficiency times management factor" for irrigation efficiency. Therefore, the management factor is accounted twice, since it is already considered in LPJmL water quantity used for irrigation (`airrig`: annual irrigation). Furthermore, the module realization does not consider annual water balances but only water balances during the growing period of crops. This period differs between cells.

### (B) all_sectors_aug13

This realization models agricultural sector water demand endogenously, as described in the first realization, Industry, electricity and domestic demand are also modelled endogenously with various scenarios; Various settings (same ias in previous realization) for environmental water demand described below.

Agricultural water demand:

Water demand for agriculture is endogenously calculated based on irrigated cropland `vm_area(j,kcr,"irrigated")` and livestock production `vm_prod(j,kli)`.

Non agricultural human water demand:

For industry, electricity and domestic demand, three scenarios are available on cluster level from the model by Alcamo et al. (2003):

- SRES A2 (WATCH Project)
- SRES B1 (WATCH Project)
- SSP2 (ISI-MIP Project)

Due to the fact that MAgPIE only considers available blue water during the growing period of the plants (43_water_availability), the fraction of this demand in the growing period is determined in the preprocessing assuming constant demand over the whole year. The matching of the WATERGAP scenarios to the MAgPIE scenarios can be found in the file `scenario_config.csv` in the config folder of model.

Environmental water demand:

Environmental water requirements can be specified separately using the switch `s42_env_flow_scenario`. The following settings are available:

- No additional environmental flows are considered.
- A certain fraction of available water `s42_env_flow_fraction` is reserved for environmental purposes and consequently not available for agricultural activities (in addition to `s42_reserved_fraction`).
- Environmental flow requirements (EFR) are calculated from LPJmL inputs according to an algorithm by Smakhtin et al. (2004) on cluster level. Due to the fact that MAgPIE only considers available blue water during the growing period of the plants 43_water_availability, EFR are also only calculated during this growing period. These are reserved in addition to `s42_protected_fraction`. In the case of the absence of an environmental flow protection policy, a base protection can be specified: `s42_env_flow_base_fraction`. It defaults to 5 % of available water.

\[\begin{multline*} vm\_watdem("agriculture",j2) \cdot v42\_irrig\_eff(j2) = \sum_{kcr}\left( vm\_area(j2,kcr,"irrigated") \cdot ic42\_wat\_req\_k(j2,kcr)\right) + \sum_{kli}\left(vm\_prod(j2,kli) \cdot ic42\_wat\_req\_k(j2,kli) \cdot v42\_irrig\_eff(j2)\right) \end{multline*}\]

`vm_watdem` is composed by irrigation and livestock demand uses. The factor `v42_irrig_eff` corresponds to the amount of water that is used inefficiently in the irrigation process.

> Limitations The module uses the "conveyance efficiency times management factor" for irrigation efficiency. Therefore, the management factor is accounted twice, since it is already considered in LPJmL water quantity used for irrigation (`airrig`: annual irrigation). Furthermore, the module realization does not consider annual water balances but only water balances during the growing period of crops. This period differs between cells.

## Definitions

### Objects

module-internal objects (A: agr_sector_aug13 | B: all_sectors_aug13)
| Description | Unit | A | B
--- | --- | --- | --- | ---
f42_env_flow_policy (t_all, scen42) | EFP policies | \(1\) | x | x
f42_env_flows (t_all, j) | Environmental flow requirements from LPJ and Smakhtin algorithm | \(10^6 m^3\) | x | x
f42_watdem_ineldo (t_all, j, scen_watdem_nonagr, watdem_ineldo) | Industry electricity and domestic water demand under our socioeconomic scenarios | \(10^6 m^3\) |  | x
f42_wat_req_kli (kli) | Average water requirements of livestock commodities per region per tDM per year | \(m^3\) | x | x
f42_wat_req_kve (t_all, j, kve) | LPJmL annual water demand for irrigation per ha | \(m^3/yr\) | x | x
i42_env_flow_policy (t, i) | Determines whether environmental flow protection is enforced | \(1\) | x | x
i42_env_flows_base (t, j) | Environmental flow requirements if no protection policy is in place | \(10^6 m^3\) | x | x
i42_env_flows (t, j) | Environmental flow requirements if a protection policy is in place | \(10^6 m^3\) | x | x
i42_wat_req_k (t, j, k) | LPJmL annual water demand for irrigation per ha per year (m^3) + Livestock demand per ton | \(m^3\) | x | x
ic42_env_flow_policy (i) | Determines whether environmental flow protection is enforced in the current time step | \(1\) | x | x
ic42_wat_req_k (j, k) | LPJmL annual water demand for irrigation per ha per year (m^3) + Livestock demand per ton | \(m^3\) | x | x
q42_water_demand (wat_dem, j) | Water consumption in different sectors | \(10^6 m^3/yr\) | x | x
s42_env_flow_base_fraction | Fraction of available water that is reserved for the environment where no EFP policy is implemented | \(1\) | x | x
s42_env_flow_fraction | Fraction of available water that is reserved for under protection policies | \(1\) | x | x
s42_env_flow_scenario | EFP scenario. | \(1\) | x | x
s42_irrigation_efficiency | Value of irrigation efficiency | \(1\) | x | x
s42_irrig_eff_scenario | Scenario for irrigation efficiency | \(1\) | x | x
s42_reserved_fraction | Fraction of available water that is reserved for industry electricity and domestic use | \(1\) | x |
s42_watdem_nonagr_scenario | Scenario for non agricultural water demand from WATERGAP | \(1\) |  | x
v42_irrig_eff (j) | Irrigation efficiency | \(1\) | x | x

### Sets

sets in use
| description
--- | ---
i | World regions
kcr(kve) | Cropping activities
k(kall) | Primary products
kli(kap) | Livestock products
kve(k) | Land-use activities
scen42 | Environmental Flow Policy (EFP)
scen_watdem_nonagr | Scenarios for non agricultural water demand
t_all | 5-year time periods
t(t_all) | Simulated time periods
w | Water supply type
wat_dem | Water demand sectors
watdem_ineldo(wat_dem) | Exogenous water demand subset covering humanly induced demands
wat_src | Type of water source

## Authors

Anne Biewald, Markus Bonsch

## See Also

09_drivers, 17_production, 30_crop, 42_water_demand, 43_water_availability

## References

Alcamo, J., P. DÖLL, T. Henrichs, and et al. 2003. “Development and Testing of the Watergap 2 Global Model of Water Use and Availability.” Hydrological Sciences Journal 48 (3): 317–37.

Rohwer, Janine, Dieter Gerten, and Wolfgang Lucht. 2007. “DEVELOPMENT of Functional Irrigation Types for Improved Global Crop Modelling.” Potsdam: PIK.

Siebert, Stefan, Petra Döll, Sebastian Feick, Jippe Hoogeveen, and Karen Frenken. 2007. “Global Map of Irrigation Areas Version 4.0.1.” Johann Wolfgang Goethe University, Frankfurt Am Main, Germany / Food and Agriculture Organization of the United Nations, Rome, Italy. http://www.fao.org/nr/water/aquastat/irrigationmap/index10.stm.

Smakhtin, V., C. Revenga, P. Döll, and et al. 2004. Taking into Account Environmental Water Requirements in Global-Scale Water Resources Assessments.