River Revival

Abstract
This is an approach paper briefly describing the hydro-geological approach to rejuvenation of rivers. It lists-out main factors responsible for decline of water table in the catchments of a river system vis-à-vis attempts to explain the probable causes responsible for river flow depletion in non-monsoon months.
The approach paper attempts to present a conceptual framework and studies for restoration of non-monsoon flow through non-monsoon ground water recharge - a hydro-geological approach for restoration of depleting flows. It also recommends sustainable river water use prioritization / allocations.
Preamble
Flowing healthy rivers are the lifelines of the dynamic water resource. Every healthy river-system performs its natural function and is a precious source of potable water. It also provides suitable environment to aquatic life.
In recent years, a major decline in the non-monsoon flow in rivers in India has been observed. Every year, the number of drying rivers is increasing and many small rivers have lost their identity. This is more pronounced in over exploited (ground water) areas having deforested and degraded catchments.
River Definition

River is a natural stream of fresh water that flows into an ocean or into a land locked water body and is usually fed by small streams (called tributaries). The tributaries join the main river, during its onward journey, forming a drainage basin. The drainage basin collects available runoff and ground water (GW) discharge. Continuous optimum flow is an inbuilt quality of a healthy river system. Perennial healthy river is a living eco-system.
River can also be defined as is a hydrological, geomorphic, ecological, biodiversity rich, landscape developing natural system that plays key role for the freshwater cycle, balancing dynamic equilibrium between snowfall, snow-mass (including glaciers), rainfall, surface water, ground water and providing large number of social and economic services to the people and serves ecosystems in its watershed.
2.1. Natural Responsibility of a River System
The natural responsibility of a river system is multifarious. The run-off uses the river course for its onward journey. The moving waters perform two functions. Under the first function, the moving water dissolves the soluble compounds and lifts loose material (rock fragments and soil etc). Under the second function, the running water transports the eroded sediments along with dissolved compounds. During transportation, it enriches the flood plane by depositing silt. In the final phase, the running river water deposits the transported detritus material to form the delta and the dissolved salts are added to the sea. The transportation of particles is selective and is controlled by their density, river bed slope and the flow velocity of running waters. It is different in different seasons and is influenced by rainfall and snow melt. River passes through different stages and tends to develop a smooth terrain. During its life, the river system continuously performs its natural function to different degree.
Drop in the flow leads to degradation of river health, unsafe conditions for the survival of aquatic life, unfavorable environment for discharge of its natural responsibility and therefore when the continuous non-monsoon flow stops, the river dries temporarily, the hydrological cycle breaks and the river loose its natural identity.

2.2. Environmental flow
Environmental flow is that optimum quantity of continuously flowing water which is essential for the discharge of river’s natural responsibility. The natural responsibility includes eco-system, safety/survival of dependent creatures and vegetation also.

2.3. Delineation of River System in India
All India Soil and Land Use Survey (AISLUS), Department of Agriculture and Cooperation, Government of India (GOI) has published a National Watershed Atlas in 1990. This atlas shows delineated and codified river catchments. This is five stage delineation subdividing major river-systems into smaller units and every unit and its sub-units have been given a permanent code number. According to AISLUS, there are 6 major water resource regions, 35 river basins, 112 catchments, 500 sub-catchments and 3237 watersheds. The sizes of these units are in decreasing order.
Water Availability in India

According to Ministry of Water Resources (GOI), India receives approximately 400.0 million hectare meters (mhm) precipitation (including snowfall) every year through. Out of this quantity, approximately 203.7 mhm is evaporated, consumed by plants and is locked in the sub-surface (soil and aquifers) formations. The total yearly run-off and ground water reserves in the country are around 196.3 mhm and 43.2 mhm respectively. The utilizable surface run-off and ground water is 69.0 mhm and 39.6 mhm respectively.

3.1. Areas with declining non-monsoon flow
Stream gauging data and observations in different parts of the country shows that there is a general decline in the non-monsoon flow in practically all river systems. The noticeable decline of flow and drying of rivers in non-monsoon period is observed in rivers drained by smaller hydrologic units (sub-catchments and watersheds). The affected areas, in general, are as given below-

1. Sub-catchments and watersheds of the major irrigation projects.
2. Rain-fed areas.
3. Down hill areas of degraded forest with depleting soil cover.
4. Heavy ground water exploitation areas.
5. Downstream of a river stretches from where large amount of flow is lifted.
6. Areas in the neighborhood of deep open cast or underground mines.
3.1.1. Sub-catchments and watersheds of the major irrigation projects.
Irrigation projects are built across rivers. Their reservoirs store run-off water brought from uplands. The uplands generally constitute small hydrologic units (watersheds, sub-catchments etc). The lands in these units are generally undulating and degraded therefore SW and GW get drained quickly. The result is moisture / water stress in the terrain and river flows deplete immediately after monsoon. The increasing GW exploitation in the uplands quickly dewaters the aquifers and therefore non-monsoon flow ceases quickly.
3.1.2. Rain-fed areas.
The term rain-fed area is used by agriculture scientists for monsoon dependent areas. Most of the rain-fed areas are hard rock areas. They have generally shallow aquifers with poor storage capacity. The natural discharge dewaters/depletes the ground water aquifers immediately after monsoon. Due to increasing GW exploitation, the water table aquifers are emptied fast and therefore their contribution to the river system is reduced. This situation, in-turn, reduces ground water contribution to larger hydrologic units in non-monsoon season i.e. reduction in quantity and duration of flow in the entire river system.

3.1.3. Down hill areas of degraded forest with depleting soil cover.
Degraded forests with low crown density generally facilitate soil erosion. The depleting soil covers provide reduced storage space for GW recharge. Maximum run-off takes place during floods. The non-monsoon contribution from such areas is low and the flow sustainability is doubtful. This situation ultimately reduces ground water contribution to larger hydrologic units i.e. reduction in quantity and duration of flow in the river system.
3.1.4. Heavy ground water exploitation Areas.
Many ground water rich areas are over exploited. This trend is increasing in GW rich units in the country. Though the aquifers are replenished every monsoon but their contribution to river flow is continuously reducing due to increasing GW exploitation. This reduction in contribution ultimately leads to reduced ground water flow to larger hydrologic units i.e. reduction in quantity and duration of flow in the non-monsoon season in the entire river system.
3.1.5. Downstream of a river stretches from where large amount of flow is lifted.
Drinking Water supply schemes of metro-cities drawing large quantities of river water often reduces the river flow in downstream. This lift ultimately reduces flow in the downstream of the river system. Similarly when the water is lifted from the river flowing in the neighboring hydrologic unit, similar effect is observed in the downstream stretch of the river flowing in the donor unit.
3.1.6. Areas in the neighborhood of deep open cast or underground mines.
Mineral extraction requires digging of earth and therefore during mineral extraction, lot of GW is collected in the mine. This GW is pumped out and released in the nearest water course. This pumping is similar to GW exploitation and therefore rivers situated in the immediate neighborhood of the mine generally face decline in the non-monsoon flow of local rivers. The released water improves flow in the downstream rivers.
River Rejuvenation Vision

Observations indicate that the river flow is sustained till the ground water released from the catchments is above river’s bed level i.e. water table is above river’s bed level. As soon as this level dips below the river’s bed level, the river dries. The flow depletion or drying of rivers is observed initially near the origin and then progressively in the higher hydrologic units. In the background of intricate behavior and dynamic function of a river-system, this approach paper attempts to provide a conceptual platform for restoration of the flow in the river system vis-à-vis river water utilization of for different purposes.
4.1. Data for River Rejuvenation
River rejuvenation is required in flow stressed hydrological units in non-monsoon season therefore the hydro-geological approach for river rejuvenation stresses the need of -
A. Flow data of a river at regular time interval during non- monsoon season at the outlet of each flow stressed relevant hydrologic unit.
B. Corresponding average water table decline (GW balance / stage of exploitation) in a contributing hydrologic unit at corresponding time interval.
C. Approximate quantity of GW required at regular time interval in non-monsoon season in the corresponding hydrological unit for river revival planning.
The hydro-geological approach recognizes the fact that decline of water table is a cumulative effect of non-monsoon GW draft, natural discharge and sub-surface flow. Empirical methods are suggested to approximately assess the value of draft, discharge and sub-surface flow.
4.2. River Rejuvenation Approach
The hydro-geological approach recognizes that in monsoon season, adequate water flows in practically every rivers so there is no need to further augment their flow. The challenge is in non-monsoon season therefore the river rejuvenation approach suggests-
1. Identification of stressed hydrological units.
2. Identification of factors responsible for depleting non-monsoon flow.
3. Data on A, B and C (refer 4.1 above).
4. Situation analysis in each hydrological unit
5. Suggestions for flow revival in the individual hydrological unit.
6. Need of scientific input and continuous efforts to refine approach.
7. Management of Climate Change
4.1.1. Identification of stressed hydrological units.
Watersheds and sub-catchments are the fifth and fourth hydrologic units (AISLUS). These units are located in higher reaches or upstream and are part of the larger hydrological unit. They are the home for small order streams. During monsoon, the streams flowing in these units carry flood waters but during non-monsoon, flow stress (flow depletion and stream drying) in the initial reaches is observed.
Flow monitoring, at suitable time intervals may be done at the outlet of all watersheds and sub-catchments by using velocity-area or any other method. Alternatively approximate run-off could be estimated by using rational formula. This exercise will identify stressed hydrological units. This monitoring shall broadly identify the flow stressed watersheds and sub-catchments and could be carried forward to larger hydrologic units. This exercise will classify hydrologic unit wise stressed and dry rivers.
4.1.2. Identification of factors responsible for depleting non-monsoon flow.
During flow monitoring, reconnaissance survey should be undertaken to identify the factors responsible for depletion of non-monsoon flow. The information thus collected shall identify the reasons (factors) responsible for depleting non-monsoon flow in the investigated hydrological unit.
4.1.3. Data on A, B and C (refer 4.1 above).
The data spelt in paragraph 4.1., is broadly needed for the river revival study. It is therefore stressed that the flow data at regular time interval during non- monsoon season at the outlet of each flow stressed relevant hydrologic unit, corresponding average water table decline (GW balance / stage of exploitation) in a contributing unit at corresponding time interval and the approximate quantity of GW required at regular time interval in the corresponding hydrologic unit may be collected / determined. Rainfall data of minimum past ten years will also be collected.
4.1. 4. Situation analysis in each unit
The situation analysis aims to assess the flow depletion trend in non-monsoon season and assess corresponding GW draft (quantity) and approximate month-wise quantity of GW needed for recharge along with identification of non-structural initiatives.
4.1.5. Suggestions for flow revival in the individual hydrological unit.
The out come of the situation analysis and interpretation of data should conceptualize hydrologic unit wise structural (desired SW and GW structures) and non-structural initiatives.
4.1.6. Need of scientific input and continuous efforts to refine approach.
Since the earth crust is heterogeneous in nature, therefore there is an unquestionable need for scientific input and continuous effort to refine the approach in different litho-units and their variations for successful restoration of flow in different hydrological units. The approach also needs assessment of relationship between agro-climates and incoming climate change effects.
4.1.7. Management of Climate Change
It is believed that the climate change is expected to influence the rainfall pattern. It may increase the flood intensity in certain pockets therefore flood management through water conservation activities would be required. Similarly, in decreasing rainfall areas, an appropriate strategy will be required to assess the probable impact of climate change on river water management activities.
4.2. Prioritizing River Water Use for sustainability of flow
Sustained non-monsoon flow advocates prioritization of wise-use of river’s water in the non-monsoon months. The suggested prioritization for the wise use of river waters in the non-monsoon flow-
• Environmental flow
• Drinking Water and basic needs.
• Water use for livelihood and agricultural (exclude water intensive crops).
• Water use for Celebrations, Public Gatherings on festivals or religious occasions, Fairs and Cultural Tourism.
• Hydro-power.
• Water intensive crops and water consuming activities.
• Industries.
• Others if any.
The river water allocations should be made after meeting the requirement of the environmental flow. The drinking and basic needs should be assessed and quantifiable allocations be made. Further allocations could be made after meeting the above requirement. The allocations for basic and other needs should be reviewed and revised every ten years following the up-to-dated census data.
Depending upon the water availability, the approach considers it appropriate (if viable) to support economic activities but it discourages non-essential water intensive / consuming activities in the water stressed or water deficit stretches.
The use of river water for meeting drinking water needs of nearby locality or city or adjoining agriculture fields or other hydrologic unit should be permitted after meeting environmental flow, drinking and basic needs.
Article Written By :-
K G Vyas
Retired Advisor , Rajeev Gandhi Watershed Mission
Rural Development Department, Govt of Madhya Pradesh
Bhopal, India

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