Trend analysis of Hydrological variables in Western Himalayan region -Phase I (JAMMU & KASHMIR)

Abstract

Western Himalayan region is the main stay of the Himalayan water tower holding more than 90% of glacier and cryospheric resources in India and abundant monsoon rainfall along its foothills. Major rivers of the region; Ganga, Yamuna, Sutlej, Beas, Chenab, Jhelum, Zanskar, Indus, Shyok and Nubra all originate from the mighty Himalayas and contribute immensely to the development of our country and our neighbouring countries. As these rivers carry abundant water to the northern Indian plains and sustain millions of people, mountain population are solely dependent on precipitation, springs and groundwater. Mountain ecosystems are identified as most vulnerable under the climate change regime and mountain communities are already facing numerous challenges to adapt with the uncertainties in the weather pattern exacerbated by the changing regime. Lack of data and knowledge in the mountain region is impacting both adaptation as well as water resources development of the region. In many areas of the western Himalayan region, water resources are underdeveloped and have enormous possibilities whereas many areas are facing problems related to water availability. The region has diverse hydrological regimes ranging from monsoon dominated lesser Himalaya and Shivaliks, snow dominated middle Himalayas and snow and glacier dominated higher Himalayas. A cold- arid region of Ladakh is another unique hydrological regime of the Western Himalaya. Water resources issues of the region are also varied reflecting the various hydrological regimes of the area. Available data relevant to the water research in these areas are highly localized and many basins have very poor data network. The western Himalayan region is spread across three states i.e. Jammu & Kashmir, Himachal Pradesh and Uttarakhand. In Stage – I, an attempt has been made in the present study to prepare a database of J&K State and to determine the trend of the various hydrological variables on seasonal and annual time scale in this data sparse region (J&K) over a long time span using non-parametric methods. Precipitation and discharge are the two major driving forces of a hydrologic regime of any river system, and changes in its pattern could have direct and indirect impacts on water resources. Changing climate due to rising GHGs concentration and subsequently global warming may alter the spatial and temporal pattern of precipitation. Change in its distribution would influence the spatial and temporal distribution of runoff, soil moisture, groundwater reserves and would alter the frequency of droughts and floods. To understand and track these changes, it is very important to analyze the trend of these hydro-meteorological variables. There are many different ways in which changes in hydrometeorological series can take place. A change can occur abruptly (step change) or gradually (trend) or may take more complex form. Climate change is often recognized as a progressive trend. Studies of precipitation change are typically complicated by factors such as missing values, seasonal and other short-term fluctuations (climate variability) and by lack of homogeneity of the data (e.g. due to changes in instrument and observation techniques). There are many approaches that can be used to detect trends and other forms of nonstationarity in hydro-meteorological data. In deciding which approach to take, it is necessary to be aware of which test procedures are valid (i.e. the data meets the required test assumptions) and which procedures are most useful (likely to correctly find a change when it is present). Chenab Precipitation The present study indicates a significantly decreasing average annual and seasonal precipitation trend over the last 40 year in Chenab basin. 20 out of 24 precipiation are supporting the declining precipitation trend in basin. It is showing a negative trend of precipitation of -6.62 mm/annum for period of 1967-2007 on annual time series basis. Only two station namely Paoni and Mou is showing increasing trend with 90% singificance level on annual basis. Chenab Discharge The discharge of the Chenab basin as a whole is showing a rising trend in winter (all 9 sations) and spring season (7 out of 9). The basin is showing a rising trend of discharge of 1.24 Cumec/annum for period of 1967-2007 on annual time series basis. Only the outlet sation Akhnoor is showing declining trend in discharge at the rate of -3.82 Cumec/annum in annual series. The maximum magnitude of positive trend was found at Premnagar (15.16 Cumec/annum) in Monsoon season. This contrary may be due to the reason that the Chenab river has a large number of glaciers in its basin, which have played a regulatory role in controlling its discharge. As the smaller glaciers have receded at a relatively faster rate than the larger ones, this may ultimately lead to their desertion in the near anticipated future. Kashmir Precipitation Annual rainfall at four stations, namely Kulgam and Handwara (during the period 1903–1982) and Qazigund and Kukarnag (during the period 1962–2002), was found to be decreasing. Srinagar station experienced a decreasing trend in annual rainfall during the period 1903–1982, whereas it experienced an increasing trend during 1962–2002 and also during 1901–2002. None of the observed trends in annual rainfall were found to be statistically significant. Rainfall in the winter season (the season which receives maximum rainfall) decreased at Kulgam, Handwara, Qazigund, Srinagar (1903–1982) and increased at Kukarnag and Srinagar (1962–2002 and 1901–2002). The decreasing winter rainfall at Kulgam and Handwara was found to be statistically significant at the 95% confidence level. Srinagar and Handwara showed similar trends (decreasing) in annual rainfall and rainy days during the period 1903–1982, whereas opposite trends (decreasing rainfall and increasing rainy days) were found at Kulgam. Observed trends in annual rainy days were not found to be statistically significant. Winter rainfall and rainy days experienced the same direction of trend (decreasing) at all three stations during the period 1962–2002. The decreasing trend in rainy days at Handwara was found to be statistically significant. The study indicates decreasing rainfall at four stations and increasing rainfall at one station in the Kashmir Valley over the period of record. If this widespread decreasing trend in rainfall is sustained, it will adversely impact the economy of the Valley. There is a need to incorporate the changing climate in planning and management of water resources of the Valley. The study also provides some scenarios of patterns of rainfall change, which may be used for sensitivity analysis of water availability in Kashmir Valley. Finally, although there are uncertainties about the magnitude and direction of future climate change at various places, measures must be initiated to minimize the adverse impacts of these changes on society. Tawi Discharge Tawi river is experiencing the declining trend in annual as well as seasonal discharges. The rate of decrease in discharge in Tawi is -0.731 cumec/annum for annual series, -0.163 for winter, -0.639 for spring and -1.070 for monsoon season at significance level of 90%. Ground water level May 2010 with respect to May 2000 – May 2009 Out of 104 wells showing decline, 78 wells (66.10 %) are showing decline less than 2 m. Decline from 2-4 m is shown by 15 wells (12.71%) and 9 wells (9.32%) are showing decline more than 4 m. Out of 12 wells, which are showing rise, all are in the range of 0-2 m. August 2010 with respect to August 2000 – August 2009 Out of 88 wells showing rise, 78 wells (59.09 %) wells are showing rise less than 2 m, 8 wells (6.06 %) are showing rise from 2-4 m and 2 wells (1.52%) are showing rise more than 4 m. Out of 44 wells, which are showing fall, 34 wells (25.76%) that have shown fall in water level are in the range of 0-2 m, 6 wells (4.55%) have shown fall between 2-4 m and Fall in the range of 2-4 m is shown by 3 wells (2.27%). November 2010 with respect to November 2000-November 2009 Out of 78 wells showing rise, 74 wells (57.36 %) wells are showing rise less than 2 m, 4 wells (3.10 %) have shown rise from 2-4 m and no well have shown rise more than 4 m. All the 19 wells, which are showing fall, are in the range of 0-2 m. January 2011 with respect to January 2001 – January 2010 Out of 83 wells showing rise, 73 wells (56.15%) wells showing rise less than 2 m, 9 wells (6.92%) have shown rise from 2-4 m and only a well has shown rise more than 4 m. A total of 39 wells (30%) have shown fall in water level in the range of 0-2 m. Six wells (4.62%) have shown fall between 2-4 m and 2 wells (1.54%) have shown fall in the range of 2-4 m.