Livestock Pressure and River Water Quality in Jombang Regency, Indonesia Based on Monitoring Records and Livestock Statistics
This study analyzes Jombang Regency's river water quality by correlating livestock statistics with monitoring data from 2023 to 2025, revealing significant exceedances in organic, nutrient, and fecal indicators that align with high livestock density and supporting targeted non-spatial pollution control measures despite the presence of other pollution sources.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Rivers are the lifeblood of a region, carrying water for drinking, farming, and washing, but they also act as the final destination for everything that washes off the land. When farmers raise animals, the waste they produce—manure, leftover feed, and the water used to clean the animals—can easily find its way into these waterways. This waste is not just dirt; it is a complex mix of organic matter that consumes oxygen as it breaks down, nutrients that can cause excessive plant growth, and microscopic bacteria that pose health risks. Scientists often try to map exactly where these pollutants come from, using computers to draw lines between farms and rivers. However, this process can be difficult if the exact locations of every farm are not known or if the data is incomplete. In such cases, researchers must look at the big picture, comparing the sheer number of animals in a region with the quality of the water flowing through it, asking a simple but vital question: does the pressure of the livestock match the pollution we see in the water?
In the Jombang Regency of East Java, Indonesia, a team of researchers tackled this question without relying on complex maps or digital models. Instead, they combined two distinct sets of records: official counts of the animals living in the area and the water-quality tests taken from the local rivers between 2023 and 2025. The region is a hub for livestock, home to millions of chickens, hundreds of thousands of goats and sheep, and tens of thousands of cattle. The rivers flowing through this landscape, including the Brantas and the Marmoyo, were monitored repeatedly over these three years. The researchers wanted to see if the patterns in the water told a story that aligned with the massive scale of animal farming nearby. They were not looking to prove that a single farm caused a specific problem, but rather to see if the general intensity of livestock activity corresponded with the types of pollution found in the water.
The water tests revealed a clear and recurring pattern of stress in the rivers. The most frequent issue was an excess of organic matter, measured by a parameter called biochemical oxygen demand. This value indicates how much oxygen bacteria need to break down waste in the water. In nearly sixty percent of the valid tests taken in Jombang, this level was higher than the recommended safety benchmark. This suggests that biodegradable waste is constantly entering the rivers, likely from sources like manure, wash water, or food scraps. Alongside this organic load, the water also showed high levels of total phosphate, a nutrient that can trigger algal blooms and deplete oxygen. Almost half of the phosphate measurements exceeded the safety limit. While the rivers did not show dangerous spikes in nitrate, a different type of nutrient, the presence of phosphorus points strongly toward sources like animal manure and household detergents. Furthermore, the water carried signs of fecal contamination. Tests for fecal coliform bacteria, which indicate the presence of animal or human waste, exceeded safety limits in about one out of every six tests, while total coliform bacteria, a broader indicator of contamination, showed even higher rates of concern in the limited samples available.
The livestock statistics painted a picture of immense pressure on the land. In 2024 alone, the regency was home to more than 16 million broiler chickens, alongside nearly 100,000 goats, over 60,000 sheep, and more than 60,000 beef cattle. These numbers did not stay static; while some populations shifted slightly in 2025, the scale remained enormous. The researchers noted that this pressure was not spread evenly. Certain districts were dominated by specific types of animals, with some areas acting as major centers for poultry and others for cattle or goats. When the researchers looked at the water quality alongside these population numbers, a logical connection emerged. The types of pollutants found in the water—organic waste, phosphorus, and fecal bacteria—are exactly the kinds of substances produced by large numbers of farm animals. If manure is left uncovered, if washing water flows directly into drains, or if waste is applied to fields just before a rainstorm, these pollutants can wash rapidly into the river system. The convergence of high animal numbers and high pollution levels suggests that livestock waste is a significant contributor to the river's condition, even if it is not the only one.
However, the study is careful to avoid blaming the animals entirely. The rivers of Jombang are also affected by domestic sewage from homes, runoff from markets, and waste from other agricultural activities. The researchers explicitly stated that their data cannot prove that a specific farm caused a specific drop in water quality, nor can they rule out other human activities as major contributors. The relationship is one of strong association rather than simple cause and effect. The presence of millions of animals creates a potential for pollution that is undeniable, but whether that pollution reaches the river depends on how the waste is managed, how the land is drained, and how the weather behaves. The study argues that ignoring livestock would be a mistake, as it is a major source of the observed problems, but treating it as the sole villain would be an oversimplification that could lead to ineffective policies.
The findings offer a practical path forward for local officials who need to protect the rivers without waiting for perfect maps or complex computer simulations. The researchers propose a straightforward strategy based on what is already known: target the districts with the highest concentrations of animals and focus on the specific pollutants that are most common. This means encouraging farmers to store manure in covered areas to prevent rain from washing it away, separating clean rainwater from dirty wash water, and treating wastewater before it leaves the farm. It also means paying closer attention to the water during the rainy season, when the risk of pollutants washing into the river is highest. By focusing on these tangible actions in the areas where the animals are most numerous, local agencies can begin to reduce the pressure on the rivers. The study concludes that while the rivers face a mix of challenges from many sources, the sheer volume of livestock in Jombang makes waste management a critical piece of the puzzle, one that can be addressed with clear, targeted efforts rather than waiting for high-tech solutions.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.