# water demand module (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 core, and the 30_crop, 16_demand and 43_water_availability modules. It passes information to the module water availability and the core.

## Interfaces¶

### Input¶

Name Description Unit A B
$im\_wat\_avail(t,wat \_src,j)$ Available water (to calculate water demand from fractions) mio. tDM x x
$im\_gdp\_pc(t,i)$ GPD per capita (gdp path for irrigation efficiency regression) US\$2004/cap x x$vm\_area(j,kcr,irrigated")$Production area (to calculate the irrigation water demand) mio. ha x x$vm\_prod(j,kli)$Cellular livestock production quantities for all livestock categories (to calculate livestock water demand) mio. tDM x x The last columns of the table indicate the usage in the different realizations (numbered with capital letters) ### Output¶ Name Description Unit$vm\_watdem(wat\_dem,j)$Cellular water demand for different sectors mio.$m^3$### Interface plot¶ Figure 0: Information exchange among modules. ## Realizations¶ ### (A) all_sectors_aug13¶ Agricultural water demand The calculation of agricultural water demand is the same as in the "standard" realization. Non agricultural human water demand For industry, electricity and domestic demand, three scenarios are available on cluster level from the WATERGAP model5: • SRES A2 (WATCH Project) • SRES B1 (WATCH Project) • SSP2 (ISI-MIP Project) The preprocessing script that extracts the WATERGAP data and converts it to MAgPIE input can be found in: http://subversion/svn/magpie/tools/watdem_nonagr  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 (see lpj2magpie). The matching of the WATERGAP scenarios to the MAgPIE scenarios can be found in the file$scenario\_config.csv$in the config subfolder of the main MAgPIE folder:  MAgPIE scenario Watergap scenario B1 B1 B2 SSP2 A1 SSP2 A2 A2 SSP1 B1 SSP2 SSP2 SSP3 A2 SSP4 A2 SSP5 A2 b2_ethics B1 Environmental water demand For environmental water requirements, the same settings as in the "standard" realization are available. Limitations The module uses a conveyance efficiency x management factor for irrigation efficiency. Therefore, the management factor is double accounted for because it is already considered in lpj airrig. 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) agr_sectors_aug13 (default)¶ Agricultural water demand Water demand for agriculture is endogenously calculated based on irrigated cropland ($vm\_area(j,kcr,"irrigated")$) and livestock production ($vm\_prod(j,kli)$).$vm\_watdem("agriculture",j) = \sum \limits_{kcr}vm\_area(j,kcr,"irrigated")\cdot ic42\_wat\_req\_k(j,kcr)) / v42\_irrig\_eff(j) + \sum \limits_{kli} vm\_prod(j,kli)\cdot ic42\_wat\_req\_k(j,kli)$Irrigation water demand per hectare for each crop category and cluster ($ic42\_wat\_req\_k(j,kcr)$) is provided by the LPJml model1 (see lpj2magpie). 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 determined from FAO sources (FAOSTAT 2005). Irrigation efficiency Different scenarios for irrigation efficiency can be chosen. All of them rely on preprocessed data by PIK Report No. 1022. The script for preprocessing can be found in http://subversion/svn/magpie/tools/irrigation_efficiency  There is a switch to choose different settings for the irrigation efficiency$v42\_irrig\_eff(j)$in the input.gms: 1. A global static value is applied. It is the global weighted average of water losses from source to field (conveyance efficiency times management factor) from PIK Report No. 1042 (Annex B). Irrigated area from Siebert et al3 has been used as aggregation weight. 2. A regression between country values of conveyance efficiency times management factor from PIK Report No. 1042 (Annex B) and GDP is performed. The functional relationship is:$v42\_irrig\_eff(j) = 1/\left(1+2.7^{\frac{-22160-fm\_gdp\_pc(t,i(j))}{37767}}\right)$Values are kept constant at 1995 levels for each region. 1. Same as 2 but scenario dependent evolution over time (see figure 1). Figure 1: 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$s42\_reserved\_fraction$in the input.gms 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 which is a vague guess. Environmental water demand Environmental water requirements can be specified separately using the switch$s42\_env\_flow\_scenario$in the input.gms. 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 LPJ1 inputs according to an algorithm by Smakhtin 20044 on cluster level (see lpj2magpie). 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. Where and when a potential environmental flow protection policy takes effect is determined in the file$EFR\_protection\_policy.csv$in the input folder of the water demand module. Limitations: The module uses conveyance efficiency * management factor for irrigation efficiency. Therefore, the management factor is double accounted because it is already considered in lpj airrig. 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¶ Name Description Unit A B$s42\_reserved\_fraction$Fraction of available water that is reserved for industry electricity and domestic use - x$f42\_wat\_req\_kve(j,k)$LPJ annual water demand for irrigation$m^3$per ha per year x x$f42\_wat\_req\_kli(j,k)$Average water requirements of livestock commodities per region$m^3$per ha per year x x$f42\_env\_flows(j)$Environmental flow requirements from LPJ and Smakhtin algorithm mio.$m^3$x x$c42\_env\_flow\_policy(i)$Determines if environmental flow protection is enforced in the current time step - x x$f42\_env\_flow\_policy(i)$EFP policies - x x$i42\_env\_flows\_base(j/flow)$Environmental flow requirements if no protection policy is in place mio.$m^3$x x$v42\_irrig\_eff(j)$Irrigation efficiency (Conveyance efficiency) - x x$s42\_watdem\_nonagr\_scenario$Scenario for non agricultural water demand from WATERGAP - x$s42\_irrig\_eff\_scenario$Scenario for irrigation efficiency - x x$s42\_irrigation\_efficiency$Value of irrigation efficiency x x$s42\_env\_flow\_scenario$Environmental flow protection scenario - x x$s42\_env\_flow\_fraction$Fraction of available water that is reserved for environmental flows globally under a protection policy - x x$s42\_env\_flow\_base\_fraction$fraction of available water that is reserved for environmental flows globally if no protection policy is in place - x x$watdem\_ineldo(wat\_dem)$Subset of$wat\_dem$containing industrial, domestic and electricity demand - x$watdem\_exo(wat\_dem)$Subset of$wat\_dem$containing exogenous water demands (industry, electricity, domestic, ecosystem) - x x$scen\_watdem\_nonagr\$ Set containing available scenarios for non agricultural water demand (A2 , B1 , SSP2) - x x

The last columns of the table indicate the usage in the different realizations (numbered with capital letters)

## Developer(s)¶

Anne Biewald, Markus Bonsch

## References¶

1 [LPJml] Bondeau, A., Smith, P.C., Zaehle, S., Schaphoff, S., Lucht, W., Cramer, W., Gerten, D., Lotze-Campen, H., Mueller, C., Reichstein, M., Smith, B., 2007. Modelling the role of agriculture for the 20th century global terrestrial carbon balance. Glob. Change Biol. 13, 679–706.

2 [PIK Report No. 104] Janine Rohwer, Dieter Gerten, Wolfgang Lucht
DEVELOPMENT OF FUNCTIONAL IRRIGATION TYPES FOR IMPROVED GLOBAL CROP MODELLING, 2007.

3 [Siebert et al 2007] Stefan Siebert, 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

4 [Smakhtin 2004] Smakhtin, V., C. Revenga, P. Döll, et al. 2004
Taking into Account Environmental Water Requirements in Global-scale Water Resources Assessments.

5 [WATERGAP] Alcamo, J., P. DÖLL, T. Henrichs, et al. 2003
Development and Testing of the WaterGAP 2 Global Model of Water Use and Availability.
Hydrological Sciences Journal 48(3): 317–337.