Distance Learning Module 3 - Rivers of the Hindu Kush, Pamir, and Hindu Raj
RIVER NAMES (Figure 3.1A, B & C)
Figure 3.1A. Map of some of the main rivers of Afghanistan showing the regional context to a few of the other rivers in the neighboring countries of Tajikistan to the north, and Pakistan to the south.
Figure 3.1B. Map of the main rivers of Afghanistan
Figure 3.1C. Map of the rivers of Afghanistan showing the master drainage systems, as well as the glacier meltwater sources (green dots, where each dot equals about 10 glacier ice masses, which are concentrated in the north and east of the country.
Kabul River System (Exorheic) (Figure 3.2)
Ghorband – Panshir – Logar – (Chitral) Kunar – Kabul – Swat – Indus – Indian Ocean
Figure 3.2. Map of the Kabul drainage system.
Helmand River System (Endorheic) (Figure 3.3)
Helmand – Arghandab – Seistan Depression – Hamoun seasonal lakes – Gaudi Zirreh
Harirud – Tenjen amd Murghab River Systems (Figure 3.4)
Hari Rud – Tenjen – Karakum Desert Kushk – Murghab – Karakum Desert
Figure 3.4. Map of the Harirud drainage system.
Amu Darya River System (Figure 3.5)
Abi Pamir – Abi Wakhan – Panj – Kokcha – Kundus – Amu Darya – Aral Sea
Figure 3.5. Map of the Amy Darya drainage system.
Kabul River System is exorheic – that is, it flows to the Indus at out into the Indian Ocean, although during some dry drought years, the Indus dries up before reaching the sea.
All other Afghanistan rivers are endorheic – they flow only into basins of interior drainage where they are used entirely in agriculture or they flow on into dune fields and desert basins where they evaporate away.
The rivers of Afghanistan are remarkable for their diversity, even as their activity is such a strong agent in the formation of fluvial landforms, whereas their waters are the critical lifeblood for the Afghan people (Table 3.1; Figure 3.6A, B, & C). The larger rivers of arid Afghanistan rise in the Hindu Kush and Pamir mountains, mainly from snow and glacier melt, and flow on fairly steep gradients to the lowlands. Maximal flows in spring and summer melt-water river-discharges are followed by fall and winter minima, when some large rivers even dry up completely. Most runoff is delivered from melting of seasonal winter snow or older glacial ice and high sediment loads are characteristic. Ephemeral stream channels abound in the lower elevations and are commonly filled by torrential summer thunderstorms so typical of many desert areas, especially where monsoon precipitation has penetrated from the south.
Rivers in Afghanistan commonly reflect three major spatial controls by location of drainage basin (Figure 3.1c): (1) the north and northwestern flow of the Nile-sized Amu Darya and several other rivers into the central Asian depressions of the Turkestan endorheic (interior drainage flow) basin; (2) the strong west and southwest flow of the Afghan-Iran Plateau endorheic basin, largely structurally controlled, with the main Helmand River into basins such as the Seistan on the Iranian border; and (3) the southeastward exorheic flow by the Kabul River and its tributaries into the Indus basin system in Pakistan. Most of these master drainages rise in the higher central and eastern part of Afghanistan where the altitude is great enough to trap moisture arriving in the westerly winds, as well as Indo-Pakistani monsoonal moisture coming from the south or southeast.
Of all the major rivers that rise in the highlands of Afghanistan, only the waters of the exorheic Kabul River reach the sea where they join the Indus at Attock in Pakistan. The other major endorheic rivers that exit the country’s borders include the Amu Darya and tributaries that form the northern border of the country and drain to the Turkestan endorheic basin with the drastically declining Aral Sea as the final sink, the Murghab and the Hari Rud in the northwest that also go to the Turkestan endorheic basin, and the Helmand in the southwest, which drains into closed hamoun depressions in the Seistan Basin (Figure 3.7A, B, C, D, & E).
These rivers all rise in the highlands from melt-waters coming from snow, or glacier and rock-glacier ice, before passing out through mountain gorges and into wider valleys where flights of abandoned stream terraces and lower altitude floodplains start to occur. Smaller drainages, generally ephemeral stream valleys, commonly flow out of the mountains where sediment discharges of varying types (stream flow, rapid, wet debris flows) at the mountain fronts result in the common alluvial fans and of dramatically different gradients and sizes (Figures 3.9, 3.10) .
Figure 3.10. Satellite view of the very large (scale bar 20 km) alluvial fan of Mazari Sharif that has been formed by human manipulation for irrigation of the Balk Ab that flows out of the mountains in the south.
Many of the alluvial-fan regions have networks of channels across them that are partly natural, and partly diversions made by human inhabitants seeking to divert seasonal water for irrigation. These alluvial fans and river floodplains grade out further into the lowlands as vast, gently sloping alluvial plains, before ending in large ephemeral lake basins or swamps, many of which are at least partly covered with dune field regs (corruption of Arabic erg to reg, as in Registan) that were mobilized out of the clastic alluvial sediments that had been brought into the basins originally by river flow into the lakes before they dried out. In prior centuries, historical records indicate that much of the lower altitude uplands in antiquity and later were well mantled with soil and extensively forested or grass and shrub covered, which would have had good effect on the beneficial infiltration of precipitation waters and slowed runoff. In addition to the dramatically increased deforestation in Afghanistan in the past three decades or so, and other forms of desertification, flooding of several kinds also seems to have increased in Afghanistan.
The hydrologic regimes of Afghanistan vary because of different runoff controls throughout the year. Thus some of the rivers have a pluvial regime, in which rain and snowmelt produce a late winter-spring maximum, and a late summer – early fall minimum when many are entirely dry. Most of the small water courses carry no water at all from April-May to November-December. Torrential pluvial regimes occur in the many dry water courses (darrah, wadi, juie, nullah) in Afghanistan, especially at times of rapid snowmelt or summer rainstorms. Rivers with a nival (snow) regime in the northeast high mountains of Afghanistan tend to have a minimum discharge in winter when they freeze strongly, and a summer maximum when the snow and ice melt. Those with a monsoon regime in the southeast also have a summer maximum, but from increasing precipitation at that time.
The estimates of the actual availability of water and its use in Afghanistan are fraught with misinformation and a high variability by as much as one third in the numbers, so much so that one suspects varieties of estimation apparently based upon what appear to be rather unreliable assumptions, or weak estimation methods, or both. In part this is because lack of reliable data collecting over the past 30 years of war, and in part perhaps also, because of changes in hydrological forecasting methods. In any case, in reference to the mean annual surface water flow of Afghanistan, or total river discharge in the country, the older estimates of the United Nations FAO were values of 55-57 billion cubic meters (bcm) for the whole country, whereas the values estimated at a slightly later time by others indicated 84 bcm. This apparent increase of 28 bcm is apparently derived from unknown citational sources but is likely not real, inasmuch as the country has been undergoing a severe drought cycle in recent years and one would expect such numbers to decline, not increase (Table 3.2).
Amu Darya River System: The Amu Darya (Oxus of antiquity) originates in the Wakhan Corridor of Afghanistan as three separate drainages, the Aq Su, the Abi Pamir, and Abi Wakhan that are confluent downstream . For example, the latter two join in the Wakhan to form the Panj River of Badakhshan, which constitutes most of the national border of Afghanistan with Tajikistan (Figures 3.11, 3.12, 3.13).
Where the Panj River is confluent with the Kokcha River from southern Badakhshan, the Amu Darya begins and goes on the form the rest of the entire southern border of Tajikistan and Uzbekistan with Afghanistan, as well as the eastern portion of the south border of Turkestan with Afghanistan (Figure 3.14).
Estimates vary because of the lack of reliable measurements or preservation of past flow records, but most of the Nile-sized flow of the Amu Darya originates in Tajikistan at about 61 percent and in Afghanistan at ~30 percent. The downstream republics of Uzbekistan and Turkmenistan combined use about 52 percent of the total flow of the Amu Darya but contribute only 9 percent of the total volume. In comparison Afghanistan currently uses less than 10 percent of its contribution (1.5 – 2 km3) and only about 2 percent of the total discharge. The average discharge of the Amu Darya appears to be around 2000 m3/s per year. The Kokcha itself, one of the major rivers of northern Afghanistan, has measured discharge rates of 108 – 163 m3/s per year, whereas the Kunduz River tributary to the Amu Darya also measures similar amounts with a mean discharge of 108 m3/s per year. All other rivers in this northernmost drainage basin of Afghanistan have waters in insufficient quantities to travel from their mountain sources to be confluent with the Amu Darya; they are diverted off for irrigation and what is left soaks into the desert sands that are peripheral to the Amu Darya.
Harirud – Murghab River System: This fluvial system represents about 12 percent of the water resources of Afghanistan and is dominant in the heavily irrigated regions around Herat (Figure 3.15).
The waters of the Harirud are mainly sourced in central Afghanistan and flow in a nearly straight westerly direction down a fault-guided valley trace toward the Iranian border, before looping north to form Afghanistan’s far northwest border with Iran, and then the river flows between Iran and Turkmenistan, before its last remnants soak into the sands of the Karakumsky desert. The Murghab River in this basin also flows out of Afghanistan into the Karakumsky desert as well, at first in Afghanistan through a strong canyon whose narrow width does not allow much room for irrigated agriculture along its banks. The average annual discharge of the Harirud is about 55 m3/s, but during a spring flood in 1939 the discharge went up to 1090 m3/s. The mean annual discharge of the Murghab was about 41 m3/s but during a flood in 1886 a discharge rate of 367 m3/s was measured.
Helmand – Arghandab River System: This important river system drains a wide region extending from the Bamiyan region in central Afghanistan, southwest into the Seistan depression and the Iranian border to encompass about 43 percent of the total land area of the nation. The Arghandab river that flows through Kandahar, joins the Helmand near Lashkargah. Two major dams in this system were built in the 1950s; the Kajaki Dam (Figure 3.7D) on the Helmand about 70 km upstream from Girishk, and the Dahla Dam on the Arghandab 50 km northeast of Kandahar. Total flow in non-drought years was estimated at about 7 km3, with mean discharges of 90 – 4000 m3/s and maxima of 18,000 – 20,000 m3/s. The main branch of the Helmand in its delta in the Seistan depression forms the Iranian border where the waters drain off in hamun (hamoon) wetlands and lakes that are discussed further below.
Kabul River System: Collectively, the Kabul River rises in the mountains of central Afghanistan west of the city, whereas its tributary, the Panshir (Figure 3.16) comes from the Hindu Kush to the northeast, and its other important feeder, the Kunar River enters Afghanistan from northwest Pakistan; collectively making up about 12 percent of the land area of Afghanistan, with about 26 percent of the annual flow of the country.
The river supports over 300,000 ha of intensively irrigated areas and high-value crops in Afghanistan. The Kabul River goes on to flow back into Pakistan just north of the Khyber Pass, where it supports some 50,000 ha of agricultural crops before its eventual confluence with the Indus River at Attock. The river has had discharges of 33 – 460 m3/s, but in recent drought years has run nearly completely dry several times in the city of Kabul with its population of ~3 million people, which is a most serious shortfall. Because of mountain snow and glacier melt waters, the Kunar River tributary (Figure 3.17) provides much of the flow in the lower Kabul where it can flow with a mean annual discharge of 700 m3/s before it enters Pakistan.
Rivers of Tajikistan: Many of the rivers of Tajikistan rise in glacier and snow melt in the Pamir Mountains that flow into the rivers of the Panj and Amu Darya (Figures 3.17 A & B).
Figure 3.17B. Map showing that the important Kunar River rises from glacier melt-water in the Hindu Raj and eastern Hindu Kush mountains in northwestern Pakistan as the Chitral River, before flowing into Afghanistan as the Kunar.
Sustainability: The sustainability of river water in Afghanistan is essential for people to survive in the future, but the future is largely uncertain for most people. Nevertheless, a number of criteria have been created to help the people of Afghanistan to better protect their water supplies (Table 3.3). These criteria should be learned by everyone and taught in the school of the country to best plan for a good future.