Blue and green water : why they affect us all

Addres­sing the water cri­sis is impe­ra­tive for glo­bal cli­mate adap­ta­tion. Cur­rent water poli­cies focus pri­ma­ri­ly on visible, or « blue, » water sources, often over­loo­king the cri­ti­cal role of « green » water, sto­red in soil and vege­ta­tion, consti­tu­ting about 60% of glo­bal land pre­ci­pi­ta­tion. Reco­gni­sing water as a Glo­bal Com­mon Good (GCG) is essen­tial for achie­ving cli­mate goals and Sus­tai­nable Deve­lop­ment Goals (SDGs).

At COP29, nego­tia­tions aim to achieve agree­ments to respond to the water cri­sis ade­qua­te­ly ; howe­ver, to do so, a pro­per unders­tan­ding of the under­lying hydro­lo­gi­cal cycle is neces­sa­ry. The water, or hydro­lo­gi­cal cycle, is unders­tood as “[…] a com­plex sys­tem with dif­ferent stores inter­ac­ting with varying strengths and over a wide range of scales with other com­po­nents of the Earth sys­tem such as atmos­phere, bios­phere, and lithos­phere¹”  and it is dri­ven by solar radia­tion and gra­vi­ty, with water chan­ging into dif­ferent states (liquid, gas, solid) and moving bet­ween the atmos­phere, ocean and land. It eva­po­rates and trans­pires from land and water bodies, then gets trans­por­ted, conden­sed, and ulti­ma­te­ly pre­ci­pi­tates back onto the Ear­th’s surface.

World­wide, we are cur­rent­ly pushing the hydro­lo­gi­cal cycle out of balance. Through human-indu­ced cli­mate change, defo­res­ta­tion, and loss of bio­di­ver­si­ty, we are chan­ging pre­ci­pi­ta­tion pat­terns. As tem­pe­ra­ture rises, the cycle inten­si­fies and eva­po­rates more water lea­ding to more extreme wea­ther events, like extreme rain­fall, hur­ri­canes and coas­tal floods². 

Cur­rent water poli­cies pri­ma­ri­ly focus on visible water sources, such as rivers and oceans (blue water), while fre­quent­ly neglec­ting the impor­tance of green water. None­the­less, scien­ti­fic evi­dence shows that around 60% of the pre­ci­pi­ta­tion that falls on land ends up sto­red as green water ‑fur­ther indi­ca­ting that green water is the lar­gest contri­bu­tor to fre­sh­wa­ter glo­bal­ly³. The impor­tance of green water is fur­ther addres­sed by Fried­ling­stein et al⁴., who high­light that green water in soils is of neces­si­ty for land-based eco­sys­tems, which can absorb 25–30% of car­bon dioxide emit­ted from fos­sil fuels.

Figure 1 repre­sents the glo­bal net­work of ter­res­trial mois­ture flows bet­ween dif­ferent regions, sho­wing how inter­con­nec­ted our world is via wind rivers. The arrows represent the direc­tion of mois­ture flow, through two pro­cesses : eva­po­trans­pi­ra­tion, the pro­cess where water is trans­fer­red from land to the atmos­phere by eva­po­ra­tion and trans­pi­ra­tion (from plants), and pre­ci­pi­ta­tion, mois­ture that returns to the land as rain­fall. There are also points pre­sen­ting the geo­gra­phi­cal centre of each coun­try to demons­trate that water eva­po­trans­pires and pre­ci­pi­tates from eve­ry coun­try towards the rest of the world. Hence, the net­work show­cases that coun­tries are high­ly inter­con­nec­ted when it comes to mois­ture flows. This is scien­ti­fic evi­dence that water eva­po­ra­ted from one region within a coun­try can signi­fi­cant­ly impact rain­fall in dis­tant regions ; coun­tries are even more inter­con­nec­ted in terms of the hydro­lo­gi­cal cycle than pre­vious­ly thought.

Simi­lar to river basins and aqui­fers, atmos­phe­ric mois­ture car­ries water from one coun­try to ano­ther, across oceans and conti­nents⁵, mea­ning that wind rivers can be tra­cked to demons­trate how eco­no­mic acti­vi­ties taking place in one region or coun­try can impact others down­wind.

For example, water eva­po­ra­tion in West Afri­ca is trans­por­ted down­wind to the Ama­zon Rain­fo­rest (most­ly Bra­zil), where it arrives in the form of rain­fall. Now, in the last decade, Bra­zil has pro­mo­ted poli­cies of hea­vy deple­tion of the Ama­zon Rainforest’s resources, which are lea­ding to a loss of green water avai­la­bi­li­ty as the land’s capa­ci­ty to store and use green water disap­pears. Hence, there is less green water that can be eva­po­ra­ted in the Ama­zon Rain­fo­rest to be trans­por­ted fur­ther down­wind to neigh­bou­ring coun­tries. This is the case in coun­tries such as Colom­bia, which rely hea­vi­ly on rain­fall water for consump­tion and ener­gy pro­duc­tion since resource deple­tion in Bra­zil has led to a lower water yield⁶. 

Glo­bal inter­con­nec­tion in the water cycle is a fact, and it means we must start addres­sing the water cri­sis holis­ti­cal­ly where both green and blue water are at the fore­front of glo­bal-scale poli­cies and pacts.

If water is part of this com­plex sys­tem cal­led the hydro­lo­gi­cal ‑or water- cycle, gover­ning it requires a shift in per­cep­tion of the way it is concei­ved. Water must be increa­sin­gly unders­tood as a Glo­bal Com­mon Good (GCG). But what exact­ly does this concept entail ?

First, reco­gni­sing water as a GCC is ack­now­led­ging that com­mu­ni­ties, coun­tries, and regions are inter­con­nec­ted, not only through visible water resources (blue water, such as rivers and lakes) but also through atmos­phe­ric mois­ture flows and green water (water sto­red in soil and vege­ta­tion). Second, this shift posi­tions water high up in the inter­na­tio­nal agen­da since it unders­tands that the Anthropocene’s impact on the hydro­lo­gi­cal cycle is intri­ca­te­ly connec­ted with the pres­sure it puts on other alar­ming pro­cesses such as cli­mate change and bio­di­ver­si­ty loss ; for ins­tance, a stable sup­ply of green water is cru­cial for absor­bing car­bon dioxide and sup­por­ting ecosystems.

Moreo­ver, this concept avoids trea­ting water in a siloed man­ner when it comes to SDGs. The water cri­sis is not only an issue to solve via SDG 6 – which most­ly deals with WASH (Water, sani­ta­tion and hygiene). Water is fun­da­men­tal to achie­ving vir­tual­ly all the SDGs since a des­ta­bi­li­sed hydro­lo­gi­cal cycle threa­tens food secu­ri­ty, eco­no­mic sta­bi­li­ty, public health, and social equi­ty, which are cor­ners­tones of sus­tai­nable deve­lop­ment⁷.

At COP29 in Baku, nego­tia­tors had a unique oppor­tu­ni­ty to pro­mote an inte­gra­ted approach to solve the water cri­sis and lay foun­da­tio­nal steps towards a uni­fied Glo­bal Water Pact by agreeing to the Baku Decla­ra­tion on Water.

During Novem­ber 19^th (the day dedi­ca­ted to food, agri­cul­ture, and water) key inputs were dis­cus­sed for the Decla­ra­tion. A cru­cial first out­come was the com­mit­ment to “[…] pro­mote dia­logue and part­ner­ships [by] streng­the­ning COP-to-COP syner­gies [and] sup­por­ting the deve­lop­ment of col­la­bo­ra­tive and ali­gned cli­mate action poli­cy⁸”. This com­mit­ment is a miles­tone in esta­bli­shing a Glo­bal Water Pact as it places the hydro­lo­gi­cal cycle as a whole at the heart of the Rio Trio – UNFCCC, UNCBD and UNCCD. After all, we know water secu­ri­ty, conser­va­tion, and sus­tai­nable mana­ge­ment must be trea­ted inte­gral­ly to achieve cli­mate goals⁹.

The Decla­ra­tion on Water, also fra­med water as a foun­da­tio­nal ele­ment in cli­mate action, as it asks coun­tries to com­mit to “[…] effec­ti­ve­ly inte­grate water consi­de­ra­tions in the desi­gn of cli­mate poli­cies, inclu­ding natio­nal adap­ta­tion plans (NAPs) or stra­te­gies, natio­nal­ly deter­mi­ned contri­bu­tions (NDCs), and asso­cia­ted imple­men­ta­tion plans, as well as natio­nal bio­di­ver­si­ty stra­te­gies and action plans (NBSAPs) […]”. Now, the decla­ra­tion was not expli­cit on the need to set clear glo­bal tar­gets rela­ted to water conser­va­tion in its green and blue forms, limi­ting the sup­port for inter­na­tio­nal pro­gress quan­ti­fi­ca­tion poli­cies, a cru­cial aspect for a well-desi­gned Glo­bal Water Pact¹⁰.

Finan­cial com­mit­ments were lacking on the Decla­ra­tion on Water. For a Glo­bal Water Pact to become a rea­li­ty, both, coun­tries and finan­cial ins­ti­tu­tions need to pledge invest­ments in sus­tai­nable water infra­struc­ture, inno­va­tive tech­no­lo­gies, and conser­va­tion efforts, which the Decla­ra­tion does not back. Addi­tio­nal­ly, the need for trans­pa­ren­cy and accoun­ta­bi­li­ty around water and its resource-rela­ted uses (such as defo­res­ta­tion and ener­gy pro­duc­tion) was not expli­cit­ly sta­ted. Hence, backing pro­po­sals such as the stan­dar­di­sa­tion of data sha­ring pro­cess, green and blue water foot­print dis­clo­sures, and sus­tai­nable cor­po­rate water prac­tices, which faci­li­tate busi­nesses’ accoun­ta­bi­li­ty in terms of impact to the hydro­lo­gi­cal cycle¹¹ becomes harder.

A big win in terms of social inclu­sion was achie­ved on the Decla­ra­tion on Water. The fif­ty signa­to­ry coun­tries agreed to include the need to incor­po­rate pers­pec­tives from often mar­gi­na­li­sed com­mu­ni­ties such as indi­ge­nous peoples, migrants and youth. A Glo­bal Water Pact will inhe­rent­ly need these voices to shape suc­cess­ful poli­cies that pro­tect local water resources in their blue and green forms and res­pect tra­di­tio­nal know­ledge since indi­ge­nous com­mu­ni­ties are ste­wards of natu­ral resources, and young people are heirs of the conse­quences of today’s water poli­cies¹².

As scien­ti­fic evi­dence proves that the hydro­lo­gi­cal cycle connects coun­tries and regions far more dee­ply than pre­vious­ly thought, a Glo­bal Water Pact seems to be the most ambi­tious, yet cru­cial way to address the water cri­sis. COP29 had a key oppor­tu­ni­ty : to ini­tiate a for­mal road­map toward a Glo­bal Water Pact by out­li­ning the role of water in cli­mate action.

By no means is this decla­ra­tion per­fect : it does not pro­mote a fra­me­work for water and cli­mate finance, and it misses the chance of backing set goals for cli­mate action. Yet, the Decla­ra­tion also sup­ports the need for COP-to-COP col­la­bo­ra­tion, pro­motes the inte­gra­tion of water – impli­cit­ly both blue and green – on natio­nal deve­lop­ment plans, and calls for the voice of indi­ge­nous peoples and youth to be at the fore­front of the debate. Ove­rall, the Decla­ra­tion on Water for Cli­mate action signed at Baku during COP29 increases the momen­tum that water has gai­ned in the past few years at the inter­na­tio­nal scale and as UNCCD (the key COP for water action) approaches, the inter­na­tio­nal com­mu­ni­ty should fol­low clo­se­ly the steps those coun­tries will take to keep increa­sing water visi­bi­li­ty on the inter­na­tio­nal agenda.