BY JEFF OPPERMAN, CHRIS WEBER, DANIEL KAMMEN

| NOVEMBER 23, 2018, 9:05 AM

In Octo­ber, the Inter­gov­ern­men­tal Panel on Cli­mate Change released a report out­lin­ing strate­gies the world can pur­sue to keep global warm­ing below 1.5 degrees Cel­sius and main­tain healthy economies and ecosys­tems. But unless we are smart about how we imple­ment that blue­print, it could cause irrepara­ble dam­age to the world’s great rivers.The panel’s report urges a rapid tran­si­tion to low-​​carbon, renew­able sources of elec­tric­ity. That call to action could trig­ger expanded invest­ment in hydropower, which is cur­rently the world’s main source for that kind of energy (70 per­cent as of 2017). But if that devel­op­ment fol­lows the pat­tern of ear­lier dam-​​building, it could accel­er­ate an alarm­ing loss of rivers and their resources, includ­ing of the fish that feed hun­dreds of mil­lions of people.The case of the Mekong River puts the prob­lem into sharp relief. The river is the world’s most pro­duc­tive fresh­wa­ter fishery—it pro­vides nearly 20 per­cent of the annual global fresh­wa­ter fish har­vest, the pri­mary source of pro­tein for tens of mil­lions of peo­ple in the region. Already, sev­eral hydropower dams on the Mekong are under con­struc­tion or are mov­ing through the plan­ning process. Sci­en­tists esti­mate that those dams, if com­pleted, will cut the river’s annual har­vest by half.

With the Mekong Delta’s sand sup­ply cut off, sci­en­tists project that it will sink and shrink, with more than half under­wa­ter by the end of the century.

The dams are also pro­jected to trap within their reser­voirs more than 90 per­cent of the sand that would oth­er­wise flow into the Mekong Delta, which is home to 17 mil­lion peo­ple and pro­duces 90 per­cent of Vietnam’s rice exports. With its sand sup­ply cut off, sci­en­tists project that the delta will sink and shrink, with more than half under­wa­ter by the end of the century.

It is easy to hear such sto­ries and con­clude that the world faces an ago­niz­ing dilemma: Must we sac­ri­fice our rivers to save our cli­mate? Even just a few years ago, that trade-​​off seemed unavoid­able. With wind and solar power lim­ited by their expense and vari­abil­ity, global hydropower was pro­jected to nearly dou­ble by 2050. Mas­sive dams were under con­struc­tion or planned for many of the world’s great rivers, includ­ing the Yangtze, Mekong, and most trib­u­taries of the Ama­zon. Some gov­ern­ments used cli­mate and renew­able energy objec­tives to jus­tify these projects, even as sci­en­tists quan­ti­fied their impacts and affected com­mu­ni­ties and indige­nous groups protested.

But we do not need to sac­ri­fice rivers for zero-​​carbon energy. In the last two years, solar energy has rapidly become more eco­nom­i­cally viable due to tech­no­log­i­cal improve­ments and to economies of scale in pro­duc­tion and deploy­ment. Whereas solar energy used to cost 20 cents or more per kilowatt-​​hour, new projects in Chile, Mex­ico, and Saudi Ara­bia have come in at one-​​tenth that cost. Wind energy costs have like­wise plum­meted. In 2017, a win­ning bid for a new wind farm in Mex­ico fea­tured costs of around 2 cents per kWh. That was half the pre­vi­ous year’s low­est bid there. This makes solar and wind the price lead­ers across much of the world.

Even with falling costs, the vari­abil­ity of wind and solar power remain a chal­lenge. Sim­ply put, in order for these tech­nolo­gies to offer reli­able, round-​​the-​​clock elec­tric­ity gen­er­a­tion, there needs to be a way to store power when the wind is blow­ing and the sun is shin­ing and then deploy it when the wind dies down or the sun sets.

For­tu­nately, the costs for stor­age tech­nolo­gies are plum­met­ing as well, with the cost of lithium ion bat­ter­ies, capa­ble of grid-​​scale stor­age, drop­ping by about 90 per­cent over the past few years. New tech­nolo­gies are emerg­ing as well. For exam­ple, a Chilean solar power plant that uses molten salt as stor­age recently offered to pro­vide 24-​​hour base­load elec­tric­ity at less than 5 cents per kWh. That is com­pa­ra­ble to or cheaper than most hydropower and fos­sil fuel options. Tesla andGoogle X, mean­while, are pur­su­ing “moon­shot” solu­tions for stor­age technologies.

Also tip­ping the scales toward wind and solar is that, among large infra­struc­ture projects, hydropower dams have among the worst per­for­mance in terms of delays and cost over­runs, in part due to the con­flict and con­tro­versy sur­round­ing them. Whereas some dams take a decade to com­plete, wind and solar power can be deliv­ered through rapid, smaller-​​scale, and lower-​​risk projects that tend to engen­der far less conflict.

Gov­ern­ments are tak­ing note. Thai­land ear­lier this year sig­naled that it would delay sign­ing a power pur­chase agree­ment for Pak Beng, a 912-​​megawatt hydropower dam that Laos is plan­ning for the Mekong. In announc­ing the delay, the coun­try stated that it needed to revisit its energy strat­egy since other renew­able sources, includ­ing wind and solar, were becom­ing increas­ingly viable. Thai­land was slated to buy 90 per­cent of the dam’s elec­tric­ity, so its change of plans could spell the end of the project. In Guyana, mean­while, ris­ing cost esti­mates and delays for the Amaila Falls hydropower project led the gov­ern­ment and financiers to trans­fer fund­ing intended for the dam toward a 100-​​megawatt solar project.

The rapidly evolv­ing renew­able energy land­scape doesn’t mean an end to hydropower, but rather a shift in its role. Hydropower reser­voirs are cur­rently the dom­i­nant form of energy stor­age for grids, and although other forms of stor­age are improv­ing, they will con­tinue to pro­vide crit­i­cal stor­age ser­vices in the near future. Upgraded older dams and strate­gi­cally planned new projects, care­fully located to min­i­mize envi­ron­men­tal and social dis­rup­tion, can empha­size energy stor­age to facil­i­tate adding large incre­ments of wind and solar into a grid.

Although it is now pos­si­ble to build afford­able, low-​​carbon wind and solar sys­tems, they still face con­straints, includ­ing polit­i­cal and social pref­er­ences for large infra­struc­ture projects. Pak Beng may have been paused, but other dam projects on the Mekong and on other key rivers are mov­ing forward.

It would be a great tragedy if the renew­able rev­o­lu­tion arrived just a few years too late to save the world’s great rivers. Mar­ket reforms and new finan­cial mech­a­nisms can accel­er­ate the adop­tion of more sus­tain­able energy sys­tems, as can inno­v­a­tive sci­ence. For exam­ple, the Renew­able and Appro­pri­ate Energy Lab­o­ra­tory at the Uni­ver­sity of Cal­i­for­nia, Berke­ley recently devel­oped and is using an energy plan­ning model for Laos. The lab found that invest­ments in solar pan­els (backed up by exist­ing hydropower) could meet that nation’s objec­tives for sell­ing elec­tric­ity to neighbors—with greater returns and lower risks than the planned dams that threaten the Mekong’s fish har­vests and the via­bil­ity of its delta.

There’s no need to con­tinue accept­ing tragic trade-​​offs between healthy rivers and low-​​cost, reli­able, and renew­able elec­tric­ity. The renew­able rev­o­lu­tion pro­vides an oppor­tu­nity to have both. Gov­ern­ments, fun­ders, devel­op­ers, and sci­en­tists should seize it.