Evolving models for integrated and sustainable management of small watersheds in semi-arid regions through investigations using modern techniques in two typical watersheds
Kolar district of Karnataka State
Longitude 13° 33' -- 13° 40'N
Longitude 77° 40' -- 77° 43'E
Spreads out in two taluks namely Chikballapur and Gudibanda.
Palakkad district of Kerala State
Latitude 11°02' -- 11°06'N
Longitude 76°35' -- 76°40'E
Lies in the Agali panchayath of the Attappady block in Mannarkadu
To establish a data bank on hydrologic and other related parameters through instrumentation and surveys, field experiments and remote sensing to serve as benchmark, and after introducing interventions to help in monitoring the changes in two typical watersheds of semi-arid region of India
To develop mathematical models to understand the hydrologic processes and to link up with other related parameters, before and after interventions
To establish a GIS for monitoring and evaluation and for developing appropriate decision support system.
The Rampatna watershed, the study area in Karnataka, covers 16.1km2 and is practically untreated. The other watershed taken up is the Payyakkara watershed having an area of 23.2 sq. km. Some areas of this watershed have been subjected to treatment. The flow in the drainage system of Rampatna watershed is active only during the monsoon periods and during the rest of the time, it is found to be dry. Indiscriminate abstraction of groundwater for domestic and agricultural purposes resulted in the depletion of groundwater source and lowering of the watertable in the Rampatna watershed. The stream flow is the main source for domestic and irrigation purposes in the Payyakkara watershed; but bacteriological contamination is noticed in this source. Monsoon rainfall is scanty and erratic in these agricultural watersheds and groundwater is primarily recharged through precipitation.
It is envisaged to systematically collect data from both these watersheds to come out with the estimation of spatial and temporal aspects of soil and water movement in these treated and untreated watersheds. It is also aimed at integrating the hydrologic and other related models with GIS for predictive purposes. The models could be regionalized for application in the semi-arid zone.
Instrumentation was carried out in both the watersheds to measure the hydrologic and meteorologic parameters such as rainfall, streamflow, evaporation, temperature, humidity, wind direction, wind speed and sunshine hours. In addition, periodic sampling and field data collection were carried out to determine the sediment movement, water table fluctuations, soil moisture status, infiltration, water quality status, physico-chemical properties of soil, geology and cropping pattern of the watersheds. The data collected were recorded in specified formats and analysed.
Detailed socio-economic surveys were conducted in the watersheds to assess the different factors and to understand the present status of the inhabitants living in the watersheds.
As a preliminary exercise, unit hydrographs from specific unit duration storms have been developed using the data from the recording raingauges, and the stream gauges established at the outlet point of the Payyakkara watershed. The available software packages were made use of for the analysis. Conventional method based on Sherman's approach, Collin's method, Conventional Nash model based on method of moments, Nash model based on optimization and Integer Nash model were also used for evolving the unit hydrographs.
An attempt was made to simulate daily runoff of the Rampatna and Payyakkara watersheds using TANK model.
Water balance studies were conducted and it is observed that water deficit conditions prevailed during most of the period of the year in both the watersheds.
The quality of water was found to be satisfactory in both the watersheds.
A GIS database was established for both the watersheds, making use of the maps and information collected from various research organisations and government departments. The maps in different scales and different levels of accuracy are digitized in ILWIS-GIS and incorporated in to a digital database. As a part of the project, a study was carried out to develop a decision support system integrating USLE model and GIS for soil conservation planning in the Rampatna and the Payyakkara watersheds.
Biophysical indicators were identified and used to monitor the changes due to the interventions.
Based on the studies and surveys conducted in the watersheds, locations of interventions for surface water development were identified and the estimate of costs worked out.
The studies indicated that there is no scope for further development of groundwater in the Rampatna watershed. Groundwater potential zones in the Payyakkara watershed was identified.
The work is expected to be useful for small watershed management programmes in the semi-arid zones.
Hydrological and meteorological parameters monitored in Rampatna and Payyakkara watersheds and the periodicity
Land utilisation and crop pattern
Well use statistics
Physico-chemical parameters of soil and water
Thematic map layers in the GIS database - Rampatna watershed (Table2
Thematic map layers in the GIS database - Payyakkara watershed (Table3
Rampatna watershed (Figure1):
The rainfall is scanty and erratic during the monsoon in the Rampatna watershed. The average annual rainfall is 800mm, of which almost 50% is received during September and October. The population growth and intensive irrigation have led to greater demand for groundwater.
The gap in demand and availability is presently met by mining the static deep groundwater storage.
The groundwater bodies are recharged mainly by direct infiltration of rainwater and to some extent through return flows from the irrigation fields and percolation from the tank beds. During most of the time, the potential evapotranspiration in the study area is much more than the rainfall. Annual evapotranspiration from the watershed is estimated as 1430 mm against average annual rainfall of 800 mm. Hence, groundwater recharge due to rainfall events is very limited.
Monthly dependable flow of more than 5 m3/sec, from the Rampatna watershed of 16.1 sq. km, is available only for 25% of the time.
In general, the groundwater quality is acceptable for irrigation and domestic needs. In a few places, fluoride and nitrate content in borewell samples is found to be slightly higher than the permissible limits. The nitrate content can be controlled by agronomic management practices. The water quality status and groundwater level changes have to be closely monitored. De-fluoridisation measures are recommended to control health hazards.
The present groundwater utilisation, as estimated for the Rampatna watershed, is about 80% of the utilizable groundwater resource of 252 ha.m and the area presently comes under the gray category (>75%) in groundwater utilisation. The projected groundwater utilisation by 2005 AD is estimated to be 96%. There is no scope for further groundwater development.
The stage of groundwater utilization in the study area has already crossed the safe limit. Therefore, for sustainable groundwater utilization in a long-term perspective, new strategies like artificial groundwater recharge, rainwater harvesting, selection of crops, which require less water and adoption of suitable groundwater management techniques have to be thought of.
Even under adverse conditions, growth rate of irrigation bore wells is alarming. Out of the total 160 irrigation borewells, 97 have been constructed during 1990-99.
About 65.15% of the total area have soil erosion values of less than 10t/ha/year and the annual average soil erosion for the entire watershed is about 22.89 t/ha/year. With suitable mechanical measures, the annual soil erosion for the entire watershed can be reduced to 13.94 t/ha/year.
The present water management practices in the watershed are not sustainable. Artificial groundwater recharge, rainwater harvesting, adoption of sustainable groundwater management techniques etc have to be thought of.
The farmers may be educated on the alarming rate of groundwater depletion in the Rampatna watershed; cultivation of appropriate crops with less water requirement may be promoted.
People's participation in watershed management has to be ensured.
Payyakkara watershed (Figure2):
Baseflow in the stream at the outlet point of Payyakkara watershed has been found to vary between 0.4m3/sec in January and 0.04 m3/sec in April/ May. The annual contribution of baseflow has been estimated as 1.0 MCM.
Based on the rainfall-recharge method, the total estimated groundwater potential is 1.5 MCM, of which only 0.5 MCM is available for utilisation, since 1.0 MCM goes as baseflow.
From a study of rainfall and evaporation loss, it is found that there is water deficit during December- May and August- September periods in the Payyakkara watershed.
From the flow duration curve, it is found that the monthly dependable flow of 40 m3/sec is available only for 75% of the time in the Payyakkara watershed.
A very high degree of sheet erosion is observed in the Payyakkara watershed; it is estimated as 114.6 tonnes/ha/year.
The quality of well water in the Payyakkara watershed is fairly good for the purposes of drinking and irrigation.
Water from the streams is bacteriologically contaminated. It is recommended to disinfect the water from the streams using bleaching powder/chlorination before drinking.
Relatively undisturbed forest areas should be given sufficient protection against grazing, firewood collection and forest fire. In addition, physical barriers live fences, fire belt etc should be established wherever necessary.
The soil and water conservation works like contour bunds, vegetative barriers, gully plugging etc should cover more area to reduce soil erosion and to improve water recharge.
Water resource development works such as storage tanks, ponds and check dams should be taken up so as to harvest the monsoon rainfall in both the watersheds. This is required to reduce the prolonged dry periods in the regions.
Date of project completion:
31st March, 2003
Total cost of project:
Rs 40.84 lakhs
Dr E J James
Centre for Water Resources Development and Management,
Kozhikode 673 571, Kerala
Phone: 2355864,2356242; Fax: 2357827