Infrastructural instabilities of urban river restoration: Towards a metropolitan political ecology in the Tel Aviv region

This article draws on the case of the Yarqon Restoration Project (YRP) in the Tel Aviv metropolitan region (TAMR) to highlight the infrastructural instabilities of urban river restoration and their theoretical implications. It analyzes the YRP as an outcome of multiple material interdependencies between “gray” and “green” infrastructures that are embedded in metropolitan-scale flows and politics. Methodologically, the article focuses on the main infrastructural projects constructed as part of the YRP and on subsequent polluting events that have since undermined the project. It uses data collected from policy documents, protocols, media coverage, and interviews conducted with stakeholders and professionals. The analysis shows that infrastructural instabilities are directly marked by the recurrence of “old” polluting uses within “new” recreational and ecological uses. These instabilities are deeply embedded in the metropolitan region’s unequal spatial-political structure, particularly disparities between upstream and downstream municipalities. We use the YRP case to develop a preliminary conceptual outline of a metropolitan political ecology, which highlights the spatial, environmental, and political complexities and inequalities of the metropolitan region and their consequences for the production of urban nature. This perspective extends the critical approach of urban political ecology, highlighting the metropolitan region as a critical scale at which natural watersheds intersect with geopolitical arrangements of territorial control, and at which environmental concerns are negotiated between numerous jurisdictions, conflicting land uses, and competing political-economic interests. The article suggests that metropolitan political ecology is a distinct and useful approach to understand not only urban river restoration but also other complex environmental issues.Keywordsurban rivers; green and gray infrastructure; pollution; metropolitan regions; urban political ecology; Yarqon river


Introduction
On July 20, 2011, the mayor of Tel Aviv-Jaffa, Ron Huldai, fulfilled his promise to swim in the Yarqon river. At that time, the river had a reputation of a polluted and toxic waterbody threatening the health and well-being of its surrounding neighborhoods and visitors. The aim of the mayor's header was to bring to public awareness the success of the Yarqon Restoration Project (YRP). The rehabilitation project sought to restore the river's ecological system and turn it into a green corridor in the dense heart of Israel's central metropolitan region. Indeed, more than a decade of efforts has succeeded in restoring, to a great extent, the river's ecology and placed it at the heart of the most popular recreational park in the Tel Aviv metropolitan region (TAMR). However, since that momentous dive, the success of the YRP has occasionally been disrupted by polluting events, often causing mass fish deaths, turbid water, and bad smells. These events repeatedly undermine the stability of the restoration project. They also raise doubts about the river's new representation as a safe, recreational green and blue space.
In this article, we draw on the case of the YRP to better understand the infrastructural instabilities of urban river restoration and their theoretical implications. We analyze between urban areas and communities (Broto et al. 2012;Wachsmuth, 2012). These metabolic processes involve complex infrastructural systems (including water and sewage) interacting with urbanized ecosystems (including watersheds and rivers). This perspective has been prolifically explored in relation to the urbanization of water as a politicized process (Gandy 2014;Swyngedouw 2004). It is also applicable to the politics of river restoration projects, which involve capital accumulation and commodification of new constructed nature (Robertson 2000), communities' resistance (Fox et al. 2012), and contested land use regimes (Chung et al. 2018).

Towards a metropolitan political ecology
As we demonstrate in the case of the YRP, understanding the interdependencies and instabilities of gray and green infrastructures in the context of river restoration requires an extended UPE -one that goes beyond the city and pays attention to the scale of the metropolitan region. Indeed, UPE suggests that urban-environmental processes are not (only) place-based, nor are they confined to predetermined jurisdictions and territories. Rather, they evolve through material and capital flows (as well as discourses) generated at and between the local and global levels. This perspective stresses that the "urban" -as a distinct space and process -is a key site for a multi-scalar investigation of the changing forms of human production and consumption of nature: "the urban process harbors social and ecological processes that are embedded in dense and multilayered networks of local, regional, national and global connections" (Swyngedouw and Heynen 2003, 899). Thus, UPE emphasizes the importance of multiple scales to understand urban-environmental processes, but, at least in its early formulation, does not prioritize a particular scale.
We seek to add a concrete metropolitan dimension to UPE's notion of the urbanization of nature, arguing that for many river basins and infrastructures, the metropolitanregional scale is paramount. In other words, urban river restoration projects cannot be analyzed exclusively at the scale of the city, not only because they usually stretch far beyond its limits, but because their proper functioning depends on a range of technical, institutional, and governance arrangements across socio-political spatialities and urban-municipal jurisdictions. We thus posit that the analysis of urban rivers generally, and the YRP specifically, calls for a metropolitan political ecology. In this sense, our analysis contributes to the more recent, and underexplored, formulation of "megapolitan political ecology," which highlights the "megapolitan" region as a particularly useful scale for understanding the function and flows of urban metabolism (Gustafson et al. 2014). Our approach is also aligned with the literature on metropolitan regions and their diverse governance arrangements across municipalities and beyond jurisdictionsespecially regarding environmental management, land use planning, and infrastructure and service provision. The challenges of environmental governance at the metropolitan scale are mainly ascribed to the prevalent spatial-political fragmentation and socio-economic disparities of large urban agglomerations, where numerous municipalities and authorities must coordinate and compete while wielding unequal political power (Thiers et al. 2017;Wheeler 2009). This has been demonstrated with regard to incoherent urban planning and infrastructure development policies, leading to suburbanization and sprawl, or with respect to the lack of efficient cross-municipal public transportation systems. Others have stressed the highly unequal social and environmental consequences of fragmented metropolitan regions, including income inequality and environmental justice/racism (Benner and Pastor 2015;Pulido 2004). On the other hand, the existence of metropolitan governance bodies, cross-municipal authorities, and/or voluntary cooperation between regional actors may consolidate policies that better address regional environmental concerns (Ahrend et al. 2014;Rosan 2016).
Both UPE and metropolitan governance thus frame our investigation of the complex political ecologies of the TAMR, as investigated through the infrastructural instabilities of an urban river restoration project. From a metropolitan political ecology perspective, the YRP is seen as negotiated between different territorial regimes, namely Israel and the Occupied Palestinian Territories, numerous municipal jurisdictions of unequal power, conflicting political-economic interests, infrastructural investments and deficits, and uneven socio-environmental processes.

The Yarqon river "salvation" and its disturbances
The Yarqon river is one of the main coastal rivers of Israel. It flows along almost 28 kilometers (km) in the dense urbanized center of the country and across seven local authorities, from the foot of the West Bank hills westward, through the TAMR, before reaching the Mediterranean. The Yarqon basin, however, stretches over 1,800 km², beyond the metropolitan region, and includes also the basin of the Ayalon stream -the Yarqon's main tributary. The larger basin, which within Israel consists of 36 local authorities and an area of over 800 km², covers over 1,000 km² beyond Israel's pre-1967 borders in the Occupied Palestinian Territory of the West Bank. In the public eye, the river is associated with the popular metropolitan recreational park -the Yarqon park -developed around its banks in the jurisdiction of the cities of Tel Aviv and Ramat Gan. At the same time, it still evokes its dubious reputation as a toxic river and an environmental hazard.

Pollution and neglect
In the pre-urbanization era of the region, the Yarqon's original high volume of fresh water flow (220 million m³/year) served several surrounding Palestinian villages for irrigation, buffalo raising, and water-power grain-mills. This included the village of Jammasin -in Arabic, water buffalo raisers -which in the 1940s neighbored the rapidly growing city of Tel Aviv. With the establishment of the State of Israel in 1948 and the forced displacement of Palestinian villages, the Yarqon river's environmental history took a gloomy turn. In the 1950s, as part of a large state-building project, Israel diverted the water source of the Yarqon, from a karst aquifer located 13 km east of Tel Aviv, towards the semi-arid southern areas of the country. The cessation of most of its spring flows was the starting point for the river's ecological deterioration from the late 1950s onwards (Gasith and Pargament 1998).
Throughout the following decades, rapid urbanization and industrialization of the river's basin -and particularly of the northern parts of the TAMR -caused severe pollution. The river effectively became drainage channel, especially for untreated sewage water from upstream localities. Further, the river channel and its surrounding areas became a destination for solid waste dumping, sand theft, criminal activities, and illegal fisheries. A routine of bad water color, smell, and mosquito breeding disrupted the well-being of the surrounding neighborhoods. The severe pollution and neglect of the Yarqon was tragically manifested during an international sport event in 1997, when a temporary bridge that was built over the river collapsed, causing the death of four athletes and injuring dozens as a result of coming in contact with riverbed toxics (Goldberg 2013).

Saving the Yarqon
Against this background, a public outcry emerged in the 1990s for the improvement of the river's ecological conditions and public safety. This was also due to a general increase in environmental awareness and activism in Israel, bringing about a shift in the legal and institutional frameworks for river rehabilitation (Tal and Katz 2012). The YRA's objectives are to rehabilitate the river's ecological system, prevent its pollution, and develop recreational landscapes along its banks. Its jurisdiction is limited to the river's channel and to a strip of 20 meters of land on each side. However, the YRA council consists of representatives from diverse governmental agencies and public organizations, to enable cooperation at the metropolitan scale and the entire river basin. The council includes eighteen members, including representatives of three government ministries, seven local authorities through which the river runs, seven corporations whose operations relate to YRA objectives, and a representative of the Israeli Land Management Authority (Pargament et al. 2010).
In 1996, the YRA board approved its first master plan, which presented a comprehensive environmental management framework for the channel within the wider basin area (Garcia and Pargament 2015a). Although not a statutory plan, it was approved that same year by the national government. In 2003, its principles were reinforced by a budgetary, schedule-based government decision. This decision put in action the "Yarqon Salvation Project" by stating detailed objectives and means for the rehabilitation of the river, prevention of upstream pollution, channel cleaning, recreational development, and the reuse of river water for irrigation. Most importantly, the master plan re-determined the river's water sources and allocations and segmented its 27.5 km into three distinguishable parts. These three segments differ in terms of water sources, water quality and quantity, and in the methodology and properties of restoration (see Figure 1).

Projections • 14. New Uses for Old Rivers: Rediscovering Urban Waterways
Infrastructural instabilities of urban river restoration: Towards a metropolitan political ecology in the Tel Aviv region

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The three parts are: 1. The so-called "clean part," fed by fresh spring water, includes the first 7 km from the river's sources up to its confluence with one of its main tributaries -the Qana stream. Currently, this part is in relatively good ecological condition due to allocation from the Yarqon's source springs by the Israeli Water Authority. While a major success of the restoration project has been the increase of the water allocation from The forming of technical and administrative arrangements with the relevant municipal sewage authorities for ensuring the river's water quality and quantity subsequently enabled the YRA and its restoration team to execute a range of activities for restoring the riparian ecological system. These included re-engineering river banks, channel cleaning, and restoring vegetation and species, including in-danger endemic fish.
Furthermore, the river restoration enhanced the development of the river corridor as part of a larger metropolitan recreational park, which now includes amenities and bridges, walking trails and bike lanes along large parts of the river banks.

Declaration of success
In 2011, the YRP was declared as a success. Following the splashing of Tel Aviv's mayor, which attracted considerable media coverage, the chief manager of the YRA stated: "This year is a turning point for the Yarqon. We see fish in places that we haven't seen before; there is almost no need for anti-mosquito treatment … there is a significant improvement" (Israeli Channel Two News, July 22, 2011). Further, in recent years, the Yarqon park has become the largest and most popular urban park in the country, attracting an estimated 5 million visitors each year (Images 1 and 2).
Hasharon. Since 2011, these plants feed this section with tertiary high-level treated water, which amounted to 12.7 million m 3 /year in 2015 (Raz 2015). Another significant achievement is the construction of a wetland facility to further purify the Kfar Sava-Hod Hasharon WWTP output and stabilize the water quality.
3. The last 4 km of the river from the Seven Mills site to the estuary are called the "salty Yarqon." In this section, the river's water is composed mainly of sea water, which penetrates the river's channel according to low and high tides -widening the channel and enabling kayaking and boating. It is the most developed section of the river and includes more than 3 km 2 of a popular recreational park, stretching on both sides of the river for about 6 km up the stream. The success of the YRP has been verified by public use rates and ecological flourishing.
In addition, recent studies, adopting the lens of ecosystem services, suggest that the rehabilitation project will result in positive net present values of approximately US$139 million over a 30-year period, particularly due to its provision of cultural ecosystem services (Garcia et al. 2016). This compares to approximately US$24 million allocated in the 2003 government decision.

The Yarqon River Salvation disturbed
However, despite the large budget and professional knowledge that have led to the relative success of its "salvation," the Yarqon river still suffers from repeated pollution events, which destabilize the entire restoration project. The YRA samples water quality approximately twice a month at five stations along the salty western section of the river. According to data presented on the YRA website, 1 since January 2016, out of 83 tests conducted, 29 samples indicated severe pollution (more than 10,000 coliform units per 100 m/l) in at least one station, while 46 showed less-severe pollution (1,000-10,000 coliform units per 100 m/l).
Images 1 and 2: The Yarqon park in Tel Aviv. Source: Nathan Marom. Beyond such routine measurements, the Yarqon has suffered from irregular pollution events that resulted in severe damage to the restoration efforts. In most of these events, a polluted effluent (such as sanitary sewer water, oils, fuel, or fire retardant) finds its way to the river through adjacent municipalities or regional drainage networks and canals. Here, one of the main challenges of urban water body restoration is also a serious concern for the Yarqon: controlling the connectivity between the metropolitan drainage network and the river, and coping with numerous drainage management bodies at the municipal and regional levels (YRA general manager, interview, June 27, 2018).
One such overflow event occurred in 2008, when a fire in a furniture factory in an industrial zone in an upstream municipality spread to a detergent factory. The huge amounts of water used by firefighters, mixed with spilled industrial detergents and fire retardants, reached the sewage system, and caused overcapacity and a total failure of the local WWTP. The result was the discharging of low-treated and untreated wastewater to one of the Yarqon's tributaries, covering the river with white thick foam for several days. As 106 tons of dead fish were collected and the entire aquatic ecological system destroyed, an official in the Israeli Ministry of Environmental Another prominent and frequent pollution source is the WWTP of the South Sharon Regional Council (SSRC), located in the northeast metropolitan area outskirts (see Figure 1). This plant was originally designed to receive 6,000 m 3 of wastewater daily from relativity small localities from the SSRC and two adjacent municipalities.
However, in the last ten years, it has received 24,000 m 3 of wastewater per day, leading to overcapacity and frequent low-treated wastewater discharge into the Qana stream. In the last several years, this WWTP was the main cause for frequent bad water events and ecological damages to the Yarqon. Residents along the river and its streams experience severe environmental hazards of bad smells and proliferation of mosquitos while the river banks often become unpleasant spaces. These nuisances have stimulated a wide public discourse, complaints, and neighboring residents' campaigns, which criticize the authorities for failing to protect the river, the park, and their environmental wellbeing. However, residents' claims and even national media attention have fallen short of bringing a significant improvement while the construction of a new WWTP is delayed. (1) the interrelations between green and gray infrastructure at the metropolitan scale, and (2) the metropolitan political ecology of upstream and downstream municipalities implicated in the restoration project and its disturbances.

Green and gray infrastructure interdependencies and instabilities
A closer interrogation of instabilities and failures in the YRP reveals that the proper operation of the newly constructed nature -as green infrastructure -is dependent on the governance of an array of gray infrastructural networks and WTTPs that are managed by diverse authorities across the metropolitan region. The following five infrastructural facilities and networks were designed to secure the stability of the YRP in general and to prevent polluted overflows in particular.
These gray infrastructures have allowed reintroducing water from natural springs into the river, as well as setting an allocation regime from new man-made sources, namely 1. Upgrading two WWTPs (Kfar Sava/Hod Hashraon and Ramat Hasharon) whose output secures the needed amount of purified water inflow into the middle section of the river. This is the primary gray infrastructure operation that the entire project is premised on, as the WWTPs are the main providers of the river's life line and its ecological restoration.
2. The construction of wetlands near the river sources to further purify the inflow of treated water from one of the WWTPs into the river. The wetlands operate as a supportive green infrastructure to improve inflow quality and to stabilize fluctuations in WWTP output.
3. A reuse water system that collects water at the end of the middle section and channels it back to the upstream clean section in order to increase inflow volume.

4.
A water collection and purifying system currently under construction just before the third, salty section to enable the reuse of river water for irrigation.
5. An array of stoppers and suspending devices designated to prevent sewage overflows from reaching the river. This includes a pumping station in the Qana channel that is designated to redirect overflows from the South Sharon WWTP to another plant. high-quality treated sewage water (see Table 1). Yet, because the project takes place in a region of water scarcity, even reused water is contested by diverse actors and land users in the northern parts of the metropolitan region, mainly for the purpose of irrigation. In 2009, the mayor of Tel Aviv-Jaffa, who serves as the chairman of the YRA, described the new constellation as a "war over water." This war, he predicted, would only intensify as the quality of WTTP output would improve significantly by 2011 and as demands for the reused water would grow: "We need to stop the processes of allocating [from the WWTPs] elsewhere and to protect the allocations to the Yarqon" (YRA council meeting, September 29, 2009).
The YRA addressed this anticipated contestation of reused water by arguing with local and national water agencies for the regulation of WWTP output in a way that would ensure a steady inflow into the river. This objective was to be supported by the construction of a water-purifying station just before the salty section of the river, which would further draw and purify water at the end of the middle section and redirect it for irrigation. This operation would effectively make the river not only a user of treated Allocation for irrigation From river -1.5 Total in river 21.5 Infrastructural instabilities of urban river restoration: Towards a metropolitan political ecology in the Tel Aviv region 19 water produced elsewhere, but also a producer of reused water and an economically efficient project (Garcia and Pargament 2015b).
Yet, at the same time, the lifeline providers of the river, the WWTPs, also embody a destructive threat to the restoration project. In case of a major failure in one of these gray infrastructures, the available outlet would be the restored river. In anticipation of such failures, project discussions early on insisted that the restored river should not become "the available natural drainer" for the entire metropolitan region ( Thus, the YRP is at once dependent on, and an ongoing producer of, numerous gray infrastructures that are dispersed along the river throughout the metropolitan region.
However, such infrastructure provision at the metropolitan scale is only one aspect through which the project's metropolitan political ecology is manifested. In the case of the South Sharon WWTP, which is currently the main pollution source to the river, the threat to the restored river stems primarily from socio-political inequalities within the TAMR between municipalities and their limited and differentiated capacity to execute planning and environmental policy, as the next section discusses.

Pollution and power flows between upstream, downstream, and transborder localities
The green-gray infrastructure instabilities of the Yarqon can only be understood at the scale of the metropolitan region as a whole. In the absence of a bridging metropolitanlevel authority, these instabilities reflect unequal capacities of urban development and environmental management between different localities in the TAMR, as well as institutional tensions and conflicts between the local and national levels. Moreover, they are affected by ongoing urbanization of existing rural and peri-urban localities, and by the development of new suburban communities. To begin with, while metropolitan suburbanization around Tel Aviv has been going on for decades, through both expansion and "leapfrogging" (Benguigui et al. 2001), in the past decade or so it has gathered force on the metropolitan margins. Primarily, this is due to Israel's high population growth (2 percent SSRC itself is a rural municipality, which includes 31 relatively small, mostly agriculture-based communities. It is located on the external ring of the TAMR and borders on the east with the "green line," which separates Israel and the Occupied Palestinian Territories. Extending over 95,000 dunams (nearly double the size of the city of Tel Aviv-Jaffa), it is a fragmented jurisdiction that fills in open spaces between the urbanized municipalities in the north-eastern part of TAMR. In the last two decades, the SSRC more than doubled its population size (from 15,000 to 32,000) due to suburbanization processes directed by national planning authorities. This includes three new "community settlements" (the "urban settlement" of Tsur Yizhak and the smaller settlements of Matan and Nirit), which effectively function as suburbs. As the head of the SSRC explained: The South Sharon Regional Council can include new suburb-like localities.
[…] But when all of a sudden, we need to include a new settlement of 3,000 units in high density construction of 15 and 17 stories … -that means 12,000 people on top of our total population of 32,000. The implication is that the Regional Council will change its character and will not be able to provide basic services properly. (Tzur 2017) Nevertheless, the failure of the South Sharon WWTP is a result not only of suburbanization within the SSRC itself and its subsequent inability to meet its growing needs, but also of the infrastructural needs and deficits of surrounding municipalities.
Significantly, it provides services also to the Arab-Israeli city of Tayibe, with a population of more than 40,000. Here, it is important to note that Arab localities in However, as the case of the South Sharon WWTP shows, unilateral environmentalism has significant disadvantages. In fact, the untreated discharge flowing from Qalqilya has been singled out by different Israeli authorities as the main source of the problem, perhaps to cover up their own inefficient measures. The WWTP's management insists that its failures stem from "the huge scale of discharge transferred to the treatment plant whose source is, among others, the Palestinian Authority and the city of Qalqilya" (Koriel 2017). While such finger-pointing at Palestinians might be politically expedient, an Israel Water Authority report shows a more nuanced reality: while more than 60 percent of the population that the South Sharon WWTP serves resides in the West Bank, this population is nearly equally divided between Palestinian Qalqilya and Jewish settlements such as the town of Alfei Menashe, considered to be part of the TAMR outer ring (see Table 2). Thus, the detrimental consequences of Israel's unilateral environmentalism -in this case, polluting the main river of its metropolitan centerare part of the wider spatialities of its control, occupation, and colonization of the West Bank (see Weizman 2007, 19). Further and importantly, the infrastructural instabilities of the YRP are embedded in an overall unequal metropolitan landscape, even if less ostensibly conflictual. The TAMR is a constellation of cities and localities that are highly unequal in their political capital, environmental conditions, and socio-spatial "distinctions" (Marom 2014). It encompasses the urban informality and infrastructural deficiency of Israeli-Arab Tayibe, the sprawling rural South Sharon settlements, the suburban mid-sized cities of Ramat Hasharon and Hod Hasharon (which grew out of earlier agricultural

Municipal authority Number of localities Population
South Sharon Regional Council 10 13,000 Tayibe -Arab-Israeli town Infrastructural instabilities of urban river restoration: Towards a metropolitan political ecology in the Tel Aviv region 24 settlements), the hyper-density and poverty of ultraorthodox Bnei Brak, and, at its center, the "global" city of Tel Aviv (see Table 3). Yet the Yarqon River "stitches" all of these localities together, making them mutually dependent in complex ways, and hence the success of the YRP is also contingent upon such material and socio-political dependencies. In the particular case of the South Sharon WTTP failure, pollution generated by upstream, poorer, peripheral localities flows through downstream, privileged, central cities -Tel Aviv first and foremost -and "spoils" their most sought-after green environments. By contrast, power mostly "flows" in the opposite direction, be it through economic advantage or political domination, seeking (but so far failing) to create conditions that would fix downstream pollution.
Thus, the infrastructural instabilities of the Yarqon and its restoration project come to reflect political-economic and environmental inequalities between the metropolitan core and its margins. They reveal multiple levels of contestations: between dense and unaffordable city centers and rural suburbanization on the margins of the metropolitan region; between marginalized Arab-Israeli towns and the state's water and sewage authorities; and between Israel's green agenda of environmental protection and its unilateral control of Palestinian localities beyond the "green line." That is why the YRP must be contextualized, as we have contended here, within the metropolitan political ecology of the TAMR.

Conclusion: Towards a metropolitan political ecology
In May 2017, the mayor of Tel Aviv-Jaffa, Ron Huldai, addressed a letter to the Minister The mayor's letter relates the controversy surrounding the South Sharon WWTP to the damage done to the YRP by reintroducing "old" polluting uses into the "new" recreational uses. It attests to the fragility of the revitalized river as an artificial, constructed nature, and alludes to the infrastructural instabilities at the heart of the restoration project: the fact that the new nature is immersed in an array of gray and green infrastructure. These infrastructures -drainage and sewage networks, treatment plants, wetlands, reservoirs, suspenders, dams, and pumping stationsserve as the river's guardians and providers -and at the same time, they embody the greatest threat for the entire restoration project. Hence, the "old" uses of rivers cannot be regarded as "part of history." Rather, they remain embodied in the metropolitan region's metabolic circulation as a latent possibility and a constant threat, one that may be unleashed in an incident of infrastructural "collapse." The mayor's letter suggests an additional, critical insight pertaining to the metropolitan political ecology of the river and its restoration. It invokes the complex politics across the river basin, whereby relatively powerful cities downstream, led by Tel Aviv, find themselves "powerless" in the face of pollution and other environmental consequences emanating upstream, from poorer and peripheral localities. The highly differentiated and extremely unequal cities and localities that make up the TAMR are entangled in a shared riparian environment, where basic hydrologic properties can unexpectedly complicate their mutual dependencies and power relations. Moreover, while we may realistically expect the particular infrastructural instabilities addressed here to be "solved" in the near future -through more infrastructural investment and technological deployment -these metropolitan structures of inequality are likely to produce more disturbances. From this viewpoint -seeing how the material connections and coordination between green and gray infrastructures are immersed in a fragmented grid of metropolitan governance -the Yarqon river becomes a prism through which the complex metropolitan political ecology of the TAMR is refracted.
From such a perspective, the case of the Yarqon river makes a significant counterpoint to one of the most basic propositions of both UPE and environmental justice -namely, that urban environments are predominantly constructed to the detriment of those with less power and capital. While these literatures usually focus on how racially ostracized groups, ethnic minorities, or other marginalized people are disproportionately more likely to suffer from a polluted or even toxic environment, in the Yarqon case, we see how river pollution that flows from disadvantaged communities in the periphery is adversely affecting the prosperous heart of the metropolis. Of course, these literatures acknowledge that environmental hazards might also impact better-off vicinities. And certainly, in the Yarqon case too, stronger municipalities like Tel Aviv enjoy much better environmental amenities than Bnei Brak, Tayibe, or Qalqiliya. Yet, it is also true that the topography and hydrology of the metropolitan region and river basin are structured in such a way that water pollution and power tend to flow in opposite directions. The issues that we have highlighted here -the problematics of material connection and metropolitan coordination of green and gray infrastructures, the challenges of environmental governance in a fragmented and uneven metropolitan field of power, and the sometimes unexpected consequences of "downstream environmental justice"are, separately but even more so jointly, manifestations of a metropolitan political ecology. We understand this as a concept and methodology that extends and complicates the critical insights of UPE on the material, social, and political dimensions of urban metabolic processes. Our notion of metropolitan political ecology pays attention to the expanded scale of the metropolitan region, which is critical for different metabolic flows (rivers included) and for many arrangements of environmental governance. At the same time, this perspective highlights the increased complexities associated with the metropolitan region, including its territorial and administrative fragmentation, its multiplicity of actors and institutions, its competing and overlapping land uses, and its socio-environmental and socio-political conflicts and inequalities. All this suggests that metropolitan political ecology is a distinct and useful approach to understand not only urban rivers restoration, but also other complex environmental issues.