Sensors on the Ciliwung

The soldering iron hissed when a drop of sweat fell onto its tip.

In a cramped stall on the banks of the Ciliwung River, seventeen-year-old Rafi Hakim knelt on cracked tiles, holding two thin wires together with his fingertip. The air smelled of engine oil, river mud, and fried shallots drifting in from a nearby warung. Outside, motorbike horns blared on the overpass above the slow brown water.

“Pass me the number twelve spanner, Raf,” his father called.

Rafi grabbed the tool from a dented metal box and slid it across the floor. Pak Yusuf lay half inside the hull of a faded blue fishing boat, wrestling with a rusted propeller shaft. Every few minutes his eyes flicked to a yellow notice pinned to a wooden post at the stall’s entrance. The paper flapped whenever a breeze crept in from the river.

Rafi didn’t need to read it again. Three months left. Twelve million rupiah in back rent. Or the landlord would reclaim the stall that had fed their family since before he was born.

He swallowed and turned back to his project. On the floor lay a length of plastic pipe, an Arduino board screwed to scrap plywood, and a cheap float switch he’d salvaged from a broken toilet tank. Thin jumper wires tangled between them.

The solder point cooled. Rafi sat back on his heels and flexed his cramped fingers. A small blue LED blinked on the board.

“Yes,” he breathed.

He tapped on his battered laptop, its screen held together with tape at one corner. Lines of code scrolled past. A number on the screen changed as he lifted the float switch up and down.

“Water level reading,” he said softly.

His father’s head appeared over the side of the boat. “It works?”

“One more test.” Rafi grinned. “Then I’ll mount it. This is number three.”

“Three sensors.” Pak Yusuf wiped sweat from his forehead with the back of his hand, leaving a smear of grease. “Enough for your competition?”

“If they all stay alive till tomorrow.” Rafi closed the laptop. “The judges want a network, not just one gadget. Three nodes minimum.”

He liked that word: network. It sounded bigger than their stall, bigger than the river. Like a web of tiny eyes watching the water.

He unplugged the board and slid the finished sensor into the plastic pipe, sealing it with silicone. Outside, the late afternoon sun turned the river into a sheet of dull orange metal. Humid air pressed against his skin as he stepped to the concrete edge.

“Don’t fall in,” his father said without looking up.

“I’m not five, Ayah.”

Rafi knelt, the concrete warm under his knees. He strapped the pipe to a bamboo pole and eased it into the water. Muddy ripples lapped his fingers. On the laptop screen, a graph began to crawl, dots marking water level and a rough turbidity estimate from the hacked sensor.

The numbers weren’t perfect. But they moved.

Across the river, tin-roofed houses leaned over the water on wooden stilts. Laundry hung like tired flags. A boy’s shout cut through the traffic.

“Hey! Hey!”

Rafi looked up. A younger boy in a faded red football jersey sprinted along a rickety walkway. A plastic crate bobbed away from him in the current, spinning toward a tangle of branches and floating trash.

Rafi grabbed a long bamboo pole and ran to the edge. He stretched as far as he could, the pole dipping into the brown water. The crate bumped against it. He hooked it, dragged it back, and caught it before it slipped past.

The boy skidded to a stop, breathing hard. “Bang, thank you! My aunt will kill me if I lose this. It’s for her satay.”

He hugged the crate. Water dripped from the slats.

“You should tie it next time,” Rafi said.

The boy nodded, then his eyes caught on the sensor blinking on the bamboo pole.

“What’s that?” he asked, stepping closer.

“River sensor,” Rafi said. “Measures water level. Helps predict floods.”

The boy’s eyebrows shot up. “Serius? Like on TV?”

Rafi shrugged. “Smaller. Cheaper. But… something like that.”

The boy edged nearer, careful of the slick concrete. “I’m Amir. From over there.” He jerked his chin toward the stilt houses. “Our kampung flooded last month. Water came into the house at night. We didn’t know. My aunt’s satay cart floated away. She still cries.”

Rafi glanced across the water. He remembered watching from the overpass as people waded through chest-deep brown waves, carrying mattresses above their heads.

“Does it warn you?” Amir asked, pointing at the sensor. “Like, before the water comes?”

“It can send data to my phone,” Rafi said. “If the level rises fast, I get an alert.”

Amir’s gaze fixed on the blinking LED. “Can it warn us too? On our side?”

Rafi hesitated. On his laptop, three icons showed on a simple map interface he’d coded: one for the lab tank, one for this stall, and a third empty spot reserved for tomorrow’s demo.

He needed three working units for the semi-final at the community STEM lab. The competition brochure lay folded in his bag, its glossy cover showing students with drones and robots. At the bottom, the JayaPalm palm-oil company logo gleamed green and gold.

Nusantara Tech Innovators. Grand prize: a full engineering scholarship and thirty million rupiah.

If he won, he could cover the rent debt in one stroke.

Three sensors. No spares.

Amir tugged at his jersey. “If we know early, we can move the beds. Put my little cousin on the higher shelf. My aunt says next time she will sleep in her shoes.”

The muezzin’s call to Maghrib began from Masjid Al-Ikhlas up the street, the sound floating over the water.

Rafi’s chest tightened. He thought of last Friday’s khutba, when Ustadh Hadi had recited, “And do good; indeed, Allah loves the doers of good.”

His fingers loosened on the bamboo pole.

“You want one?” he asked quietly.

Amir blinked. “One what?”

“A sensor.” Rafi swallowed. “Tie it under your walkway. I’ll show you how to read the numbers on your phone. If the water rises fast, you’ll see it.”

Amir stared as if he’d offered a gold bar. “But… you need it for your project, right? My cousin told me. You’re the genius boy from the lab.”

Rafi looked at the three icons on his screen. Looked at the yellow eviction notice. Looked at Amir’s bare feet, the cracked rubber of his flip-flops.

He unstrapped the nearest sensor, the cable cool in his hands.

“Projects can be fixed,” he said. “People’s beds… harder.”

He pressed the still-damp pipe into Amir’s arms. “Tie it under the walkway, where the water is deep. I’ll add your kampung to the app.”

Amir clutched the sensor. “Serius? For us?”

Rafi nodded.

A grin spread across Amir’s face. “I’ll tell my aunt you saved her satay twice.”

He sprinted along the riverbank, sandals slapping on the concrete, the white pipe under his arm. The adhan rose to its final phrases as he vanished between two shacks.

Rafi watched him go, the space in his box where the third sensor had sat now empty. His chest felt tight.

His laptop screen showed a new icon blinking to life near the stilt houses.

Two sensors left.

He closed the lid, wiped his hands on his jeans, and headed toward the masjid with his father.

The next morning, the city smelled of frying tempe and wet dust.

Rafi pedaled his old bicycle through Jakarta’s narrow lanes, the two remaining sensors clacking in his backpack. Motorbikes weaved around him. A bus coughed black smoke as it roared past. Overhead, the sky was a flat white lid.

He turned into the alley leading to the community STEM lab, a low building squeezed between a tire shop and a photocopy stall. Inside, ceiling fans pushed hot air in slow circles. Walls were covered with circuit diagrams, faded posters of satellites, and hand-drawn rockets.

“Rafi!”

He looked up. Kak Dina, the lab coordinator, waved from behind a stack of plastic chairs. Her hijab was smudged with whiteboard marker.

“Judges come in one hour,” she said, checking her watch. “Set up your demo tank. Don’t flood the lab again.”

“That was one time,” Rafi protested, but he smiled.

He set his backpack on a table and pulled out the two sensors. He fixed one inside a clear plastic tank connected to a slow-running tap; the other he left coiled beside his laptop, labeled “Field Unit – Ciliwung.”

On the screen, his app showed three dots along a stylized river. Two glowed green near his stall and the lab. The third, at Amir’s kampung, flickered between green and red.

He frowned. The graph from that node looked jagged, with peaks in the middle of the night.

The lab door banged open.

“Bang Rafi!” Amir stumbled in, dripping river water onto the tiles. His shorts were splashed to the knees.

“Careful, you’ll short my circuits,” Rafi said, pulling his backpack away from the puddle.

Amir shoved his cheap phone into Rafi’s hand. “Look! The numbers went crazy last night. But no rain. My aunt said the sky was clear. Why like that?”

On the tiny screen, the same spikes glared back.

Rafi’s annoyance faded. He opened his laptop and pulled up the raw data. Two columns: turbidity and conductivity. Both were much higher at Amir’s sensor than at his father’s stall, especially around midnight.

“Maybe your cousin was jumping on the walkway,” Rafi muttered, but he didn’t believe it.

“What if the river is sick?” Amir asked. His voice dropped. “My little sister has red spots on her legs from the water.”

Before Rafi could answer, a hand rested on his shoulder.

“Everything okay?” Kak Dina asked. “Judges will want a smooth story, ya?”

Rafi nodded. “Just… strange readings from the kampung node.”

She leaned closer, eyes scanning the screen. “Those values are high. Near a factory?”

“There’s a big wall and some tanks near Amir’s place,” Rafi said. “I haven’t checked close.”

“Be careful,” she murmured. “Our sponsor doesn’t like… surprises.”

She glanced toward a poster on the wall: JayaPalm’s logo above the words “Building a Greener Future with Our Youth.”

Rafi looked back at the red spikes.

“Can we go see?” Amir whispered.

Rafi should have been rehearsing his explanation of flood thresholds. Instead, he heard himself ask, “Kak, can I step out for twenty minutes? Before the judges?”

She checked the time, then his face. “Twenty. Not twenty-one.”

Outside, the heat slapped them. Amir led the way along the riverbank, sandals slapping on packed dirt. They passed a concrete wall rising from the river’s edge, topped with barbed wire. A small metal sign read: “JayaPalm Processing Substation 7.”

At the base of the wall, half-hidden by weeds and trash, a pipe jutted out, trickling cloudy water into the river. Grayish foam clung to the surface. Flies hovered above it.

Amir wrinkled his nose. “It always smells like that at night.”

Rafi crouched, rolling up his jeans. He dipped his fingers into the water near the pipe. A thin oily film clung to his skin.

He pulled an empty bottle from his backpack and filled it, watching the cloudy liquid swirl.

“Come,” he said. “We test it.”

Back at the lab, he grabbed a basic sensor array from the shelf. He poured river water from near his father’s stall into one cup, Amir’s sample into another, and ran the probes through both.

Numbers flashed on the small display. The kampung water showed far higher readings.

“See?” Amir said. “Sick.”

Kak Dina watched over his shoulder, lips pressed together. “This is… concerning,” she said. “But today, focus on floods. Sponsors are in a good mood. Don’t make them… less good.”

The lab filled with the scrape of chairs and chatter as judges from the district office arrived, clipboards in hand. Rafi wiped the whiteboard clean, his mind racing.

He had a choice. Remove the kampung sensor from the display, show only neat green graphs, and talk about flood prediction. Or leave the third icon, messy and red, and risk questions.

He glanced at Amir, who stood by the door, hair still damp, watching the laptop.

“You said it would warn us,” Amir said softly.

Rafi’s fingers hovered over the delete key.

He let his hand fall.

When his turn came, he explained his system, voice steady. He pointed to the three nodes, described how they sent data over a cheap wireless link, how his app turned numbers into early warnings.

One judge frowned at the red spikes. “Is that a bug?” she asked.

“It’s from a different part of the river,” Rafi said. “Near some industrial runoff. The sensor is… honest.”

The judge scribbled. Another asked about cost. A third nodded at his use of recycled materials.

As they left, one of them said quietly, “JayaPalm’s Mr. Bima will likely want a closer look at your data before the finals. Be prepared.”

Rafi’s mouth went dry.

Rain clouds piled over Jakarta’s skyline that afternoon.

Rafi sat alone in a glass-walled meeting room attached to the lab, his laptop open. Posters of smiling children planting trees stared down. Outside, students packed up their projects, laughter and clinking tools muffled by the glass.

An email had arrived an hour ago: he was through to the finals at the city convention hall. Shortlisted for the JayaPalm Green Innovation award. A line mentioned a “special briefing” with JayaPalm’s public relations manager.

The door opened.

A tall man in a crisp batik shirt stepped in, followed by a younger assistant with a tablet. The man’s hair was neatly parted, his smile practiced.

“Rafi, yes?” he said, extending his hand. “I’m Bima Santoso from JayaPalm. First, congratulations. Impressive work for a student.”

Rafi shook his hand, feeling a firm squeeze.

“Thank you, Pak.”

They sat. The assistant placed a branded folder on the table.

“We are excited,” Bima said, “to support young innovators like you. Flood prediction is a big issue. Very aligned with our corporate social responsibility.” He gestured toward the laptop. “May I see your live network?”

Rafi opened the app. Three icons glowed on the river map. One pulsed red.

Bima’s eyes went straight to it. His smile thinned.

“And this node?” he asked.

“Riverside kampung,” Rafi said. “Near your Substation 7.”

He clicked. The pollution values appeared: turbidity, conductivity, time-stamped spikes around midnight.

Bima tapped the table with one finger. “These are… interesting numbers.”

Rafi said nothing.

“Our facilities,” Bima continued, “follow all regulations. We invest heavily in treatment. Sometimes, student prototypes misread things. Electrical noise, calibration errors. You understand.”

“For the finals,” Bima said, folding his hands, “we want you to shine. Focus on your core flood-warning capability. Use data from your stall, from the lab. Reliable, clean.” He smiled again. “Mark this third node as a calibration test. Or remove it. No need to confuse the judges with unverified pollution claims.”

The assistant’s tablet screen glowed with his graphs.

“In return,” Bima went on, “we can offer an internship at our research center. A strong recommendation for the Nusantara Tech Scholars scholarship. I read about your father’s boat stall in your application.” He tilted his head. “Hard-working family. It would be a shame if… financial pressure stopped your education.”

Rain began to drum on the glass roof.

Rafi’s throat felt tight. “If I show the data as it is?” he asked.

Bima’s smile did not change, but something behind his eyes cooled. “Then you risk misunderstanding, bad publicity, tension with partners. The scholarship committee values… alignment. Think carefully.”

He stood. “You don’t have to answer now. Upload your presentation by tonight. After evening prayers, perhaps. We will review.”

He left, the assistant gliding behind him.

Silence settled, broken only by the rain.

On the screen, the red icon blinked calmly.

Rafi’s phone buzzed. A message from Dr. Laila, his physics teacher and mentor: Don’t forget, upload slides by 7 p.m. Proud of you. Also, breathe.

Another from his father: Maghrib soon. Join me at Masjid Al-Ikhlas? I’ll wait.

He checked the time. Close to sunset. If he stayed, he could polish his slides, hide the third sensor, and upload a safe file before the deadline. If he left, he’d have less than an hour afterward.

His cursor hovered over the “Remove node” option.

Outside, faint through the rain and glass, the adhan for Maghrib began.

Rafi closed the laptop.

He stood, slung his bag over his shoulder, and locked the meeting room door.

He jogged through the damp streets, the smell of wet asphalt in his nose, heading toward the masjid’s lights.

Ceiling fans whirred above the worn green carpet of Masjid Al-Ikhlas. Men and boys lined up shoulder to shoulder. The air was thick with the scent of damp clothes and a trace of perfume.

Rafi slipped into the second row beside his father, still breathing hard. His shirt clung to his back.

“All okay?” Pak Yusuf whispered.

Rafi nodded, though his chest felt like a tangled wire.

The imam, Ustadh Hadi, began the prayer. Rafi moved through the motions. In sujud, forehead pressed to the carpet, he felt the roughness against his skin, heard only his heartbeat and the soft rustle of fabric.

His lips moved without sound. In that small dark space, he asked Allah for help.

Help me choose what pleases You. Help me with this river, this data, my father’s stall, the scholarship. I don’t know what to do.

After the prayer, people shuffled toward the shoe racks. Some stayed seated, fingers moving over prayer beads. Ustadh Hadi sat near a pillar, giving a short reminder. His voice carried just enough to reach the back.

“‘O you who have believed, be persistently standing firm in justice, witnesses for Allah, even if it be against yourselves or parents and relatives…’”

Rafi’s fingers tightened on his knees.

The ustadh spoke about truth as a trust. About how hiding harm to people and land was a betrayal, even if it seemed to protect family for a while.

Rafi stared at the carpet pattern. His mind filled with images: Amir’s little sister scratching red spots on her legs, the foamy slick by the factory pipe, his father’s tools laid out on the stall floor, the yellow eviction notice.

Outside afterward, under a dripping gutter, Pak Yusuf wiped rain from his face.

“The landlord came again,” he said, almost casually. “Said someone else wants the stall. I told him we’re trying.” He glanced at Rafi, forced a smile. “Don’t let it crush you. Allah sends provision from places we don’t expect.”

The words landed heavier than any threat from Bima.

On the walk back, streetlights flickered on, reflecting in puddles. Rafi’s phone vibrated: twenty-eight minutes left until the upload deadline.

He did not turn toward the lab.

Instead, he ducked into a small warung with a flickering “Wi‑Fi Gratis” sign. The owner nodded at him, barely looking up from the TV. Rafi ordered a sweet tea he barely tasted and opened his laptop.

The competition portal counted down in the corner.

He arranged his slides. First: an overview of Jakarta’s floods. Second: his low-cost sensor design. Third: the map.

He dragged in all three data sets. The graphs looked uglier now that he planned to show them to a hall.

His mouse hovered over the delete key on the third dataset.

Amir’s face flashed in his mind, eyes wide at the blinking LED. The oily film on his own fingers. Ustadh Hadi’s recitation.

Rafi whispered, “Bismillah,” and left the data untouched.

He added a single bullet at the bottom of the slide: “Suspicious pollution readings near industrial outflow. Further investigation needed.”

He zipped the raw file and attached it in the appendix.

When he hit “upload,” his hand trembled. The progress bar crawled. A red warning appeared: Large file. Expect delay.

The clock ticked down. At three seconds, the portal flashed green: Submission received.

Rafi exhaled.

Almost without thinking, he opened a new tab. He searched for the environmental blog link Kak Dina had once shared.

“Citizen Science Jakarta – Report Pollution.”

He clicked. A simple form appeared. Name (optional). Description. Upload files.

He typed: I am a student building flood sensors on the Ciliwung. My data shows unusual pollution near a JayaPalm substation. People nearby have skin rashes. Please investigate.

He attached the same graphs and a photo of the outflow pipe he had taken.

For name, he wrote only: Rafi, student.

He hesitated over the phone number field, then entered it.

He pressed send.

The form disappeared. The warung TV crackled with a soap opera. Outside, a motorcycle hissed past on the wet street.

Two minutes later, his phone rang.

“Assalamu alaikum,” a calm voice said. “Is this Rafi? I’m Farid, from Citizen Science Jakarta. I saw your report. Can we talk?”

The moon hung hazy behind thin clouds when they reached Amir’s kampung that night.

Rafi stepped carefully along narrow wooden planks, the river gurgling black below. Neon from distant billboards smeared across the water. The air smelled of damp wood, frying fish, and something sour near the factory wall.

At the kampung entrance, a wiry man with a flashlight waited. His hair was threaded with gray, his T‑shirt worn thin.

“This is Pak Darto,” Amir said. “He leads our RT.”

“Assalamu alaikum,” Rafi said.

“Wa alaikum salam.” The man’s handshake was firm. “You’re the sensor boy?”

Behind them, a slightly overweight man in glasses adjusted the strap of his camera bag. “And I’m Farid,” he said. “You can call me Bang Farid.” He held up his phone. “Ready when you are.”

They moved in a small group toward the factory wall. Children peered from doorways. A woman in a flowered dress rocked a baby on her hip, watching.

At the pipe, the trickle of cloudy water was steady, though the sky had been dry. Foam gathered in a pale line.

Farid filmed, kneeling to capture the outflow, then panning to Rafi’s sensor blinking under the walkway.

“Tell me what we’re seeing,” he said.

Rafi cleared his throat. “This node has been recording high turbidity and conductivity at night. Higher than upstream. The pattern doesn’t match rain events.”

Pak Darto stepped into the frame. “Our children get rashes,” he said. “Fish die. We complain, but no one listens. If this boy’s gadget makes someone listen, good.”

Farid nodded. He interviewed Amir, who pointed proudly at the sensor and described the night the numbers “went crazy.”

A small crowd gathered, murmuring in the damp air.

Farid took water samples in labeled bottles, photographed the pipe, the kampung, the blinking LED. He asked Rafi to email him the raw data.

“Tomorrow is your competition, right?” Farid said as they walked back. “Are you ready for some noise?”

Rafi thought of the convention hall, the banners, Bima’s thin smile, his father’s tired hands.

“I don’t know,” he admitted.

Farid’s mouth quirked. “Good data speaks loudly. Sometimes louder than we plan.”

By morning, the data was shouting.

Rafi sat on his bed, back against the peeling wall, phone in his hand. The small fan above him rattled. His mother moved quietly in the kitchen, the smell of fried egg and rice seeping under the door.

On the screen, an article glowed: “Student’s River Sensors Expose Factory Waste on Ciliwung?”

The photos showed the outflow pipe, the foam, a blurred shot of his sensor. His name was not written, but the words “senior high schooler from South Jakarta” and “community STEM lab” were there.

Comments piled beneath the post. Some praised the anonymous student. Others argued about jobs and development. A few defended JayaPalm.

Rafi’s stomach twisted.

His phone buzzed again. A message from Kak Dina: You saw the article? Brace yourself. Sponsors will be tense today. I’m with you.

Another from an unknown number: From JayaPalm. We expect professionalism at today’s event.

He dressed in his cleanest shirt, smoothing the collar with slightly shaking hands.

At the convention hall, bright banners hung from the ceiling. JayaPalm logos sat above every stage. Rows of booths lined the floor, students in matching uniforms arranging posters and prototypes.

Rafi’s display looked small among the drones and polished robots: a laminated title sheet, three printed graphs, two sensors on stands, and a looping video on his laptop of the river rising during last month’s flood.

“Looks solid,” Dr. Laila said, appearing at his side. Her eyes were tired but warm. “Whatever happens, this work matters.”

Before he could answer, security guards moved past, making a path. Bima approached, jaw tight, phone in hand.

He stopped just inside the booth, lowering his voice. “You spoke to the media?”

“They contacted me after I used a public tip form,” Rafi said. His palms were damp.

“You mentioned our facility by name.” Bima’s tone was flat. “Without consulting us.”

“I mentioned what the data shows,” Rafi said.

Bima glanced around, then stepped closer. “Listen carefully. In your presentation, you will say your prototype is not accurate for detecting pollution sources. You will call the readings a possible calibration error. You will not link them to JayaPalm. If you do this, we can still support your scholarship application. We can still donate equipment to your lab. If you don’t…” He let the sentence hang.

Through a gap in the booth wall, Rafi saw his father entering the hall, wearing his best shirt, still stained with old grease. His eyes wandered over the displays, pride and curiosity mixed.

A volunteer handed out programs. Rafi caught a glimpse of his own name under “Green Innovation Finalists.”

Over the PA system, a cheerful voice announced that Ms. Ratna from the Nusantara Tech Scholars program was in attendance, “looking for bright minds to support.”

Rafi’s heart pounded.

He thought of the twelve million rupiah debt. Of his mother counting rice. Of his father’s smile when he talked about Rafi becoming an engineer.

He also saw Amir’s kampung, the narrow planks, children playing inches above polluted water.

“Your session is in ten minutes,” Bima said. “Decide.”

He walked away.

Rafi wiped his hands on his trousers. Dr. Laila stood a few paces back, watching his face. She didn’t ask what had been said. She just gave the smallest nod.

When his name was called, his legs felt light as he climbed the small steps to the stage. The hall buzzed, then quieted. Judges sat in a row. Bima and two other JayaPalm representatives occupied the front seats. Farther back, he spotted his father, hands clasped.

Rafi adjusted the microphone.

He clicked to his first slide. “My name is Rafi Hakim,” he began. “I live by the Ciliwung River. It floods our neighborhoods often. I wanted to build something simple that our communities can afford, to warn us before the water reaches our doors.”

He spoke about float switches and cheap electronics, about using scrap materials so even small stalls and kampungs could have sensors.

Then he tapped to the map slide.

Three nodes glowed.

“This is my test network. One sensor by my father’s boat stall. One in a controlled tank at our community lab. One in a riverside kampung across from us.”

He pointed to the graphs. “These lines show water level and basic indicators of water quality over several nights.”

He zoomed in on the third node’s data. The jagged spikes filled the screen.

“Here,” he said, “we see repeated increases in turbidity and conductivity at night, even when there is no rain. This node is located near an industrial outflow pipe from a facility labeled Substation 7.”

A murmur rippled through the hall.

“My prototype is simple,” he continued. “It cannot, by itself, prove legal violations. But it can show patterns. These patterns suggest continuous discharge into the river at night. People living nearby have skin problems. Fish die. I believe this deserves proper investigation by authorities with better equipment.”

He let the words hang, not looking at Bima.

One judge scribbled. Another leaned toward her colleague. Someone in the back took a photo of the screen.

Rafi finished by describing how the same network could send early flood warnings via text to low-cost phones. He thanked the judges and stepped back.

Applause came, scattered but real.

He walked off the stage, his ears full of his own pulse.

Back at his booth, he tried to steady his breathing. Students milled around, some throwing him curious glances. Amir, who had somehow slipped into the hall, bounced on his toes near the back wall, grinning.

Bima approached, face unreadable. He did not speak. He went straight to the judges’ table, signed a form, and walked away.

An hour later, as students gathered for the awards, Rafi’s cracked phone buzzed. An email notification slid down the screen.

From: Nusantara Tech Innovators Committee.

He opened it.

Due to violation of sponsor communications protocol and unauthorized dissemination of sensitive preliminary data, your project is disqualified from all JayaPalm-sponsored awards. Your recommended status for the Nusantara Tech Scholars scholarship is withdrawn for this year.

His vision blurred around the edges of the screen.

He felt a hand on his arm. Dr. Laila peered at the phone, then at his face. She didn’t say anything. She just stayed there.

A shadow fell over them. Rafi looked up. His father stood there, chest rising and falling a little faster than usual.

Rafi turned the phone so he could see.

Pak Yusuf read the email slowly. His jaw tightened for a second. Then he took a long breath, closed the message with his thumb, and folded Rafi’s fingers gently around the device.

He placed his other hand on Rafi’s back, warm and solid.

“Come,” he said quietly. “They will announce their prizes. We will listen. Then we go home. We still have a river.”

The evening air by the Ciliwung was thick with the smell of rain and grilled corn.

Rafi sat on an overturned paint bucket outside his father’s stall, the yellow eviction notice still pinned nearby, its corners curling. Inside, Pak Yusuf hummed a nasheed under his breath as he tightened a propeller bolt, metal clinking softly.

The old radio on the shelf crackled. A newsreader’s voice broke through the static.

“…following public concern and viral footage from a student-led citizen science project, the environmental agency has ordered a temporary shutdown and inspection of a JayaPalm substation’s waste outflow into the Ciliwung…”

Rafi froze, the screwdriver in his hand halfway to the toolbox.

“…residents of a riverside kampung say they hope the investigation will address recurring health issues and fish deaths. A spokesperson for JayaPalm declined to comment pending the inspection…”

In the background of the clip, faint but clear, he heard cheers and someone shouting, “Hidup kampung kita!”

Amir’s voice.

Rafi set the screwdriver down carefully.

A motorbike pulled up outside the stall. Kak Dina swung off, pulling off her helmet, cheeks flushed from the ride. She carried a bulging backpack.

“Busy hero?” she said lightly.

Rafi shook his head. “Disqualified hero.”

She smiled, but her eyes were serious. “Maybe. But some people noticed.”

She pulled a folded paper from the backpack and handed it to him.

He unfolded it. The letterhead bore the name of a local university’s engineering faculty.

Dear Rafi,

We learned of your flood sensor project and your recent presentation. We are impressed by your initiative and technical ability. We would like to invite you to join our environmental engineering lab as a volunteer research assistant during the upcoming break. While we cannot offer a scholarship at this time, we can provide mentorship and support you in applying for a needs-based fee waiver exam next year, independent of any corporate sponsor.

Sincerely,

Prof. Arman

Rafi read it twice. There was no instant solution to twelve million rupiah. But there was a lab. Real equipment. A path that did not run through JayaPalm.

He handed the letter to his father.

Pak Yusuf read it slowly, lips moving. Then he nodded once, eyes shining just a little.

“Allah closed one door,” he said, turning back to the half-fixed motor, “and opened a window. We will see what blows in.”

He picked up his wrench.

On the riverbank, a small group of neighborhood kids had gathered. Amir stood among them, waving a coil of cheap cable like a trophy.

“Bang Rafi!” he called. “Come! We got enough money for another sensor!”

Rafi blinked. “From where?”

“People online,” Amir said proudly. “Bang Farid put your graphs on his blog. Some uncles sent donations. Enough for parts.” He held up a plastic bag rustling with components: a float switch, some resistors, a small board.

Kak Dina laughed softly. “Looks like your network is growing.”

Rafi grabbed his toolbox. “Ayah, I’m going to the bridge.”

His father waved the wrench without looking up. “Go. Don’t drop my pliers in the river.”

Rafi joined Amir and the kids. Together they walked toward a low concrete bridge near the edge of the kampung. Motorbikes crawled over it, engines buzzing. The river gurgled below, dark and restless.

They knelt by the rail. Rafi slid the new board into a length of PVC pipe, threading the cable through, his fingers moving with practiced confidence. Amir handed him zip ties one by one.

“Here, hold the flashlight,” Pak Yusuf said behind them.

Rafi glanced back, surprised. His father had wiped his hands and followed, a small torch in his grip. He shone the beam on their work, the light trembling slightly on the water.

Across the river, tin-roofed houses glowed with dim bulbs. The sky above them deepened to indigo.

From Masjid Al-Ikhlas, the call to Isha began, the imam’s voice rolling over the water, threading through the night sounds.

Rafi gripped the pipe. “Ready?” he asked.

Amir nodded, eyes bright.

“Satu,” Rafi counted. “Dua. Tiga.”

Together they lowered the new sensor into the murky river. Cold water splashed his knuckles. He tightened the last zip tie around the bridge rail, pulling until the plastic bit into his palm.

He took his aging phone from his pocket and handed it to Amir.

“Open the app,” he said.

Amir tapped. The screen lit his face. A new icon blinked to life on the map, joining the others already watching the river’s moods.

“Got it,” Amir whispered.

The adhan’s final words echoed over them.

Rafi tugged once more on the cable, checking the knot. His hands were steady.

He straightened up, wiped mud on his jeans, and turned toward the masjid’s glowing doorway with Amir at his side, the river murmuring quietly below the bridge.