Water Footprint

Question 1

Three examples of Water Footprint

Answer 1

• Water accounting & vulnerability evaluation (WAVE)
• Fate of evaporation and implications for water footprinting
• Available Water Remaining (AWARE)

Question 2

WAVE Inventory

Answer 2

WCeff=FW-WW-ER-VR

WC=effective water consumption
FW=Freshwater withdrawals
WW=Wastewater discharges
ER=Evapo(transpi-)ration recycling
VR=Synthetically created vapor recycling

Question 3

BIER

Answer 3

Basin internal evaporation recycling

Question 4

BEER

Answer 4

Basin external evaporation recycling

Question 5

Basin Internal Evaporation Recycling (BIER)

Answer 5

Evaporation Recycling: ER=EBIERa

𝛼=𝑟𝑢𝑛𝑜𝑓𝑓/𝑝𝑟𝑒𝑐𝑖𝑝𝑖𝑡𝑎𝑡𝑖𝑜𝑛

BIER changes over the year

λ- Ø length scale of evaporation recycling ->tells us which average distance one drop travels after it has been evaporated before it comes back as rain
x -Size of drainage basin, assumed to be quadratic -> the bigger the drainage basin the more internal evaporation recycling

Question 6

WAVE - Impact assessment

Answer 6

• Impacts are defined as the risk to deprive (entrauben) other users of using freshwater when consuming water: RFD=(WCeff*WDI)
• Water Deprivation Index (WDI) denotes the vulnerability of a basin n to freshwater deprivation and, thus, expresses the potential to deprive other users when consuming water in basin n and month k

Question 7

WAVE - Impact assessment - 6 Steps to calculate WDI

Answer 7

WDI= water deprivation index (Wasserentzugsindex)

Step 1:
Ratio of water consumption (C) to water availability (A) - 𝐶𝑇𝐴=𝐶/𝐴

Step 2:
Consideration of surface water stocks (SWS)

Step 3: Consideration of groundwater stocks (GWS)

Step 4:“Translation” of water scarcity
into vulnerability regarding
freshwater deprivation

Step 5:
Absolute water shortage

Step 6:
Total WDI=max(WDIrelative;WDIabsolut) –>worst case analyse

Question 8

Step 2

Answer 8

Consideration of surface water stocks (SWS) in CTA=C/A+SWS

SWS=(Vdam+[Alake/wetland*d])/100 years

• Volumes of dams available in
  WaterGAP3 (Eisner, S. 2016)
• Volumes of lakes and wetlands are determined by multiplying their surface areas (WaterGAP3) with an effective depth (5 m lakes, 2 m wetlands)
• In order to combine volumes of surface water stocks and annual flows of consumption and availability, an anually usable fraction of 1% is assumed

Question 9

Step 3

Answer 9

Consideration of groundwater stocks

𝐶𝑇𝐴∗∗=[𝐶/(𝐴+𝑆𝑊𝑆)]∙𝐴𝐹𝐺𝑊𝑆

– In contrast to surface water stocks, groundwater stocks cannot be quantified
– Adjustment factor are developed based on geological structure and groundwater
recharge WHYMAP, Richts et al. 2011)

Question 10

Step 5:

Answer 10

Absolute water shortage
– WDI(Water deprivation index) for absolute water shortage determined based on aridity (Trockenheit) index (pot. evapotranspiration/
precipation(Niederschlag))

Question 11

Integrated WAVE factor

Answer 11

• Combining BIER and WDI into an integrated WAVE+ factor, which can simplify
the application if evapo transpi )ration is dominant form of water consumption

WAVE+=(1-BIER)*WDI
with 1-Bier=Water accounting part and WDI=impact assessment part

• BIER, WDI, WAVE factors are determined on a monthly and basin resolution;
to increase applicability, they are aggregated to:
– Annual basin specific averages
– Annual country averages
– Annual world region averages

Question 12

Available Water Remaining (AWARE)

Answer 12

• Building a consensus model for assessing
  impacts of water use in LCA
• Stressbased generic midpoint

Question 13

Evolution of scarcity indicators modeled in LCA

Answer 13

Availabilty - demand

Question 14

AWARE Characterization Model

Answer 14

AMD=(Availability-Humand demand - ecosystems demand)/Area

Question 15

AWARE Characterization Model

Answer 15

CF=AMDworld-avg/AMD

CF=max=100, if demand>availability or AMD<0,1*AMDworld

CF=Min=0.1,if 0.1 AMD_i ≥ AMD_world or AMD_i ≥ 100 AMD_world