Why Do We Measure the River Flow in Skardu?

1. Where is Skardu?

Skardu, this intriguing city in the Gilgit - Baltistan region of northern Pakistan, is a geographical wonder encompassed by some of the most breathtaking mountain ranges on the planet. It lies at the confluence of the Indus River and the Shigar River, at a height of around 2,500 meters above sea level. Surrounded by the giant Karakoram, Himalaya, and Hindu Kush mountains, Skardu's topography is characterized by massive mountains, extensive valleys, enormous glaciers, and desert oases at high elevations. This abnormal topography makes the city a cold-arid climate with extensive and harsh winters and intense snowfall, but otherwise relatively brief and moderate summers. The unforgiving climatic conditions and rugged terrain not only shape the local topography but also play a paramount role in controlling the hydrological cycle of the area.

Skardu is culturally an ethnically diverse melting pot of numerous ethnic groups and cultures. The region is dominated by Balti people, whose culture draws its roots deep into ancient Tibetan - Buddhist traditions and also the Persian and Central Asian cultural traditions. This is reflected in the melody-abundant traditional building melody within the region, such as the ancient Kharpocho Fort that sprawls over the city with a fusion of the traditional technique of construction and ancient monuments. Traditional music, dance such as the Rouf, and handicrafts such as hand-woven woolen carpets and hand-crafted wooden items are reflected within the regional culture. Skardu is also a significant tourist spot, being frequented by tourists and nature enthusiasts from around the world who come to witness its breathtaking scenery and participate in its vibrant cultural life.

The major river systems of Skardu include Indus River and the Shigar River. Indus River, which is one of the longest rivers of Asia, has its sources in the Tibetan Plateau. It flows through the high-altitude regions, gathering water from a number of glaciers and tributaries along the way before it arrives in Skardu. The Shigar River, which originates from the glaciers of the Shigar Valley, joins the Indus River near the city. The rivers are the lifeline for Skardu. They are the prime source of fresh water for domestic use, agriculture, and grazing animals. In agriculture, the water from these rivers is used to irrigate crops, thus enabling the cultivation of crops such as wheat, barley, apricots, and apples, which are a staple of the regional economy. The rivers also have immense potential for hydroelectric power generation, something that is crucial in meeting the region's growing energy demands and fueling economic growth. The rivers flowing also support a unique aquatic community, with rich fish and other aquatic life highly diversified in the cold-water environment. Where Indus and Shigar rivers confluence, there is an active ecological region impacting the flow of nearby flora and fauna, along with the regional total biodiversity.

2. How is the River Flow Near Skardu?

Influence Factors

• Precipitation and Runoff: The climate of Skardu, being at a high elevation and in a mountainous region, has restricted precipitation. The precipitation in the form of snowfall takes place mostly in the winter season and rare rainfall in the summer months. However, the glaciers and snowmelt are the primary sources of water resources for the rivers. With the increased warmth of the summer months, the great snowfields and ice sheets in the adjacent mountains gradually get melted, adding to the rivers with abundant water. Seasonally very high runoff from melting snow is produced, with peak flows between late spring and early autumn. On the contrary, during winters, when snowfalls are plentiful and temperature decreases significantly, the rivers experience low flows, and some small tributaries freeze. Runoff also depends on the extent of snow cover last winter, the rate of temperature acceleration in the spring, and the overall health of the glaciers, which are under strain from climate change.
• Topography and River Morphology: The topographic and hilly character of the Skardu terrain has a profound impact on river flow. The rivers are overflowing deep, narrow gorges and canyons in the mountain areas with steep slopes producing rapid - flowing, turbulent streams of high erosive potential. On approaching the valleys near Skardu, the slopes become lower in some sections, and the rivers widen but still retain vigorous currents due to the high volume of water. The bottoms of the river are made up of a mixture of rocky, gravelly, and sandy materials, which affect the roughness and resistance to flow. There are boulders, melting-season icebergs, and other natural obstacles that make the flow patterns even more intricate, creating areas of faster-flowing water, whirlpools, and slow-moving eddies. These physical characteristics not only determine the speed and direction of water but also the sediment transport and deposition, constantly reshaping and shaping the river channels over time.
• Reservoir Operation: Currently, there are minimal large - scale reservoir operations affecting the rivers around Skardu directly. However, with increasing focus being laid upon the development of the hydropower resources of the region, more dams and reservoirs are proposed. In the years to come, such reservoirs will play a key role in regulating river flow, filling up during peak-flow periods, and releasing the water during periods of low flows to supply a more stable water supply for the various uses. They will also help to mitigate the impact of glacial lake outburst floods, which is a potential threat in the area due to the existence of huge glacial lakes.

Historical Hydrological Events

Glacial lake outburst floods (GLOFs) pose a significant threat to Skardu and the surrounding landscape. Due to the presence of plenty of glaciers, glacial lakes are developed as ice melts and collects behind natural ice and moraine dams. Some of the events of GLOFs have taken place in the past. For example, according to studies on the Karakoram region's glacial hazards, in case of a rupture of such natural dams, they result in sudden and severe floods. The floods can sweep away bridges, roads, and settlements along the riverbanks, destroying infrastructure on a mass scale and taking lives. The floods also disrupt the transport network, contaminate water sources, and impart long-term impacts on the local economy and the environment. River flow monitoring is essential to determine the early signs of likely GLOFs and other flood-related events, as well as controlling the impacts of droughts, which even affect the availability of water in the region due to reduced glacier melt and meager precipitation.

3. How to Observe the River Flow in Skardu?

Traditional Methods

• Surface Drift Float Method: Surface drift float method is a basic method applied to estimate river flow. A float such as a buoy or wood is placed on the surface of the river. Surface water velocity can be estimated by using the time covered by the float over a known distance. It has a number of shortcomings. In the cold, swift, and generally turbulent rivers of Skardu, wind and surface turbulence will easily distort the motion of the float, and therefore measurements of velocity are in error. It also provides data only on the surface flow, while the velocities at different depths within the water column could be very different, especially for deep and wide rivers like the Indus. These limitations reduce the reliability of the method to obtain precise and accurate flow data in Skardu's challenging river conditions.
• Anchored Boat Method (Manning Table/Current Meter): Under the anchored boat method, a boat is anchored to a specific location within the river. A current meter is then lowered down to various depths in the water in order to measure the velocity of water at varying points within the vertical profile. This method can provide detailed information regarding the flow at a specific cross - section of the river. However, boat maneuvers in Skardu's rivers are very difficult due to high currents, low water temperatures, and presence of ice and large stones. The method is very time - consuming, labor - intensive, and involves high risks of safety for the operators. Repeating the measurements at different points along the river to acquire complete knowledge regarding the flow is a time-consuming task, expensive, and a job demanding professional skills, which makes frequent and repetitive measurement uneconomical.

Introduction to ADCP: Acoustic Doppler Current Profiler

The Acoustic Doppler Current Profiler (ADCP) offers a newer, more effective, and safer way to measure river flow in Skardu. In contrast to conventional techniques, ADCP can assess the water velocity at several depths at once, giving a continuous water column profile. It is non-invasive in nature, not requiring direct physical contact with the water, which is particularly crucial in Skardu's cold and dangerous river conditions, minimizing equipment destruction and operator risk. ADCP can collect enormous amounts of data over a short period of time, which can be suitable for comprehensive river surveys and real-time monitoring. This is also a consideration that matters in Skardu, where the complex river systems, extreme climatic conditions, and risk of hydrological disaster pose the need for accurate and timely flow monitoring to allow for more efficient water management, regulation of floodings, and environment protection.

4. How Does ADCP Based on the Doppler Principle Work?

The ADCP is based upon the Doppler principle. The ADCP broadcasts acoustic pulses into the water column. The pulses bounce off suspended solids within the water, such as sediment and plankton. In moving water, the frequency of the backscattered acoustic pulses changes. By precisely measuring this frequency change, or Doppler shift, the ADCP can calculate the velocity of the water at different depths. The device has multiple transducers that transmit and receive sound signals in different directions. This enables it to measure the three-dimensional velocities of the flow within the water column accurately. The information is then translated using sophisticated algorithms to develop detailed flow maps and profiles of the river. In the case of Skardu rivers, such information is valuable in understanding the complex flow dynamics that are influenced by the unique topography and climate, therefore allowing for more precise prediction of flood activity, sediment transport, and overall behavior of the river system.

5. What Does High-Quality Measurement of River Flow in Skardu Need to Have?

Equipment Requirements

• Material Reliability: Owing to Skardu rivers' harsh environment, with low temperatures, high current, abrasive sediment, and potential ice impacts, superior ADCP hardware must be built using highly reliable materials. The product must be corrosion resistant, freezer resistant, and impact resistant. These include strong metals having corrosion resistant coatings and high-resistant polymers that can withstand very low temperatures. These are preferred for ensuring the long-term and accurate operation of the ADCP in the extreme environment. This reliability is required to offer reliable and accurate flow information in the long run, which is critical to ensure effective water resource management and disaster mitigation in Skardu.
• Light Weight and Small Size: The country surrounding Skardu's rugged and inaccessible terrain demands that ADCP equipment be as light in weight and small in size as possible. This allows for easier transport and deployment, especially in outlying areas where access may be restricted to poor mountain roads or even on foot. A compact and light ADCP is easily portable by researchers and technicians, and they can measure different points of measurement on the rivers, including even those in remote valleys and gorges. Portability ensures that all significant components of the river are measured, and therefore a more comprehensive image of the river flow dynamics within the region is derived.
• Cost - Effectiveness: Cost - effectiveness is a key factor to be considered while selecting ADCP equipment for Skardu. Having limited funds at our disposal for hydrological monitoring of the region, choosing equipment that provides high - quality performance at an affordable cost is essential. Low-cost ADCPs can be used in higher quantities and on a more frequent basis, such that sufficient data are collected to form the basis for successful water management, assessment of flood risk, and decision-making. This will allow the authorities and scientists to better respond to and prepare for hydrological events, safeguarding the lives and livelihoods of the inhabitants of Skardu.

6. How to Choose the Most Suitable Current Measurement Instruments?

Methods of Deployment

• Boat - Mounted (Moving Boat) ADCP: A boat - mounted ADCP is suitable for conducting detailed surveys in rivers, discharge measurement, and flow map generation in Skardu. Though it is hard to shift a boat in the rivers of the area, where feasible, this type of ADCP can measure high reaches of the river quite quickly and provide an overall impression of the flow conditions. It is appropriate for original surveys as well as for exploration of overall flow patterns of Indus and Shigar rivers in order to assist researchers in determining abnormal flow behavior areas, flood-prone areas, or hydropower development suitable areas.
• Bottom - Mounted (Fixed) ADCP: For continuous long-term observation of river flow, a bottom-mounted ADCP is the most appropriate option. It may be installed at important locations in the river and measure flow data around the clock for decades. It is particularly useful in Skardu to monitor long - term trends, seasonal variations, and influence of variables such as climate change on the river flow. Real-time collection of data helps detect the first signs of potential hydrological activities, such as a change in the trend of flow which may be a sign of an approaching glacial lake outburst flood or a significant change in water availability due to reduced glacier melt.
• Ropeway ADCP: If ropeways are available over the river, measurement can be achieved by using a ropeway ADCP. This method is especially useful in Skardu, where the terrain and adverse conditions of the river could render boat navigation impossible or extremely hazardous. A ropeway ADCP offers precise profiling of the river flow over the entire width of the river with detailed information to be used in a variety of hydrological studies, water resource planning, and infrastructure works, such as the construction of bridges and dams.

Working Frequency

The selection of working frequency in an ADCP is an extremely important consideration. A 600 kHz ADCP typically has about a 70-meter range and is therefore useful for very shallow to medium-depth rivers. A 300 kHz ADCP has a range of up to 110 meters, which is preferable for the deeper parts of the river. Higher frequencies provide better resolution but less range, while low frequencies provide greater range but worse resolution. The frequency to be employed will need to be determined by the specific characteristics of the river, such as depth and how fine a detail is required in the measurement.

Brand Recommendations

Globally, well-known brands of ADCPs include Teledyne RDI, Nortek, and SonTek. These brands are well-known for their quality products, state-of-the-art technology, and consistent performance. However, if one desires a low - cost option, the ADCP manufacturer Chinese brand "China Sonar Panda ADCP" is an ideal choice. This "economy ADCP" is made of all - titanium alloy material, which is extremely robust and corrosion - proof. It is extremely cost-saving, hence applicable for a wide range of uses, from small-scale research work to neighborhood water management projects. For more information, you can visit their site at https://china-sonar.com/.

Here is a table with some well known ADCP instrument brands and models.